This question seeks evidence to support or refute a scientific theory.
 I won?t disclose what the theory is, but here are my relevant
questions:

1.  Did socks disappear in the laundry prior to the advent of fitted sheets?
2.  What is the comparative incidence of sockal disappearance in
households with and without fitted sheets?

There is some evidence to support the notion that the phenomenon long
predates modern convenience-based adaptations in household linens.  An
obscure and only partially decoded reference in Plato's personal
journal has been interpreted as a reference to a point of contention
between Socrates and Xanthippe, to wit:  that she was responsible for
the loss from the clothesline of one of his favorite pair, a green
plaid (literally, "hue of verdure as with crosswise furrows drawn"),
long before the infamous bucket-dumping incident.  (For recent
scholarship on this subject, see http://www.snopes.com.)

Naturally, I am interested only in supportable and verifiable data.

Thank you,
Archae0pteryx

Dear Tryx,
I have this from my Scandinavian parents, so it cannot be referenced
to Greek sources, but it may be just as old  - but still also an
explanation for that very typical and timeless marriage dispute.
Single, individual socks began to "go lost" when husbands discovered
that their wives cast all sorts of aspersions at (on?) them when they 
- the wives -  discovered a hole in the toe of one sock, to wit:  "You
should cut your toenails!" or "You forgot to wear them on the other
foot," (to spread the wear to both corners of the toes of the socks,
or simply: "You should have changed your socks sooner," (as if
spreading the wear to other pairs would reduce the overall problem).
In old Norse, this doesn't sound so aggressive, but in ancient Greek 
- delivered by the sharp-tongued Xanthippe -  it could drive arrows in
the heart of a loving husband, but not those of Cupid.
Wily Plato, anticipating from previous attacks on the subject, and
being all too  aware of the hole  - and that the attack would follow
her washing, and darning with madder-dyed yarn to emphasize her effort
 - also to let Plato's hangers-on in the Agora know that he was really
just a slovenly old tosslehead -  had his favorite youth slip into the
garden and steal the so well marked sock.

Actually, those green Argyle socks were not at all his favorite pair,
but Xanthippe had knitted them for his fifthieth birthday, and he  -
loving husband -  had praised them unduly and worn them as often as
possible in the hope that they would soon go the way of all earthly
things.

Plato had almost succeeded, but Xanthippe's tirade after the incident
forced him to continue to wear the one sock with whichever one he
happened to pull from the drawer.

This is the origin of the story about absent-minded professors who
turn up to lecture with mismatched socks.  Only the fewest of them
know that they are upholding a tradition of such long standing.

John Finley, Eliot Professor of Greek Literature, could have confirmed
this, but but very unfortunately he is no long with us.
http://www.news.harvard.edu/gazette/2000/05.25/finley.html 

Best regards, Myo

Tryx,

It is my theory that socks which disappear from dryers in our universe
have traveled through an interdimensional rift which leads to dryers
in some other universe. Somewhere, at this very moment, some slimy
bug-eyed entity is probably grumbling to its mate, "Where the frabble
do all these strange little knitted artifacts come from, and why do
they keep showing up in our tentacle-garment-drying appliance?"

~Pink

Tryx,

Fitted sheets do indeed have a way of gobbling things up, but I look
to a different source for most of the sockal disappearances.  I think
we have to blame Benjamin Franklin.  When he invented electricity he
never should have invented the static variety.  When you pull clothing
out of the dryer, static electricity kidnaps unwary socks and secretly
binds them to shirts and pants.  Some of these will escape your
detection and you will discover you are missing socks.  Sometimes you
will think to look in the closet and discover them hanging on your
shirts and pants.  But if you miss one of them, a few days later the
static electricty will release the sock and it will fall to the floor
of the closet, never to be found again.

Ansel

Socks and sheets should be treated with rules more rigorous than Apartheid

For a technical discussion see Glass and Plinkelwasser's dissertion on crotch rot.

Successful avoidance of what is in the UK called 'Public School Rot',
also known as 'Dhobi Itch', generally results in a diminution of the
quantity of unmatched socks.

The Ossowandski technique of comparison of similar, but not identical
batches, reduces the percieved 'orphan factor' to two per wash.

Basically, wash socks separately, buy them in bulk and keep the
blighters well away from anything - especially underwear, shirts and
sheets.

I think Frde-ga's above reference is from a translation with a
misspelling of the name of the famous Prof. Dr. Dr. P. P.
Pinkelwasser, whose area of study has been noted as an amusing example
of "nomen est omen".

Thank you all.  I will go a little further and mention that the
interpretation of Plato's oblique reference to Soc's sox has (as I'm
sure Prof. Finley would have been well aware) been vigorously debated
between scholars at Oxford and Cambridge, with one vocal fringe
minority asserting that Edward de Vere was actually the author of the
so-called ?verdure? story.  However, others claim that that notion is
a hoax invented by some students of Wittgenstein.

A related though somewhat less rancorous debate on sockal phenomena
has raged for decades between certain members of the faculties of
Harvard and Yale, but without producing a supportable theory that
could be systematically explored.  That honor belongs to MIT, which
has published several scholarly papers asserting something fairly
close to PinkFreud's theory; with, however, the significant difference
that the preponderance of the evidence is tending toward the idea that
there really is no missing sock; rather, the presumably orphaned sock
is a solitary *arrival* in the dryer through interdimensional means
and that we simply assume one was lost or abducted because we have an
expectation of seeing two when we see one.  Here is an instance where
we are misled by a cultural assumption, and this is why the
distinctive pair of Socrates' has significance.

Of course, in that instance, we may be seeing effects of entirely
separate causes, such as Myo suggests.

My own modest contribution to the thinking on this subject is to
suggest that the phenomenon is by no means limited to socks.  It
affects other underthings, principally men's (shorts, undershirts,
etc.), and certain other items, usually of cotton, but is seldom
detected because no one actually knows how many such articles are in a
given laundry.  It is only because the socks typically come in pairs
that we think we have experienced a loss when an even number goes in
and an odd number comes out.  Consider for a moment whether you would
really notice the addition or subtraction of one dishtowel, for
instance, or an extra washcloth in the linen closet, and you will see
that this explanation is distinctly possible.

Ansel, I enjoyed your contribution, and I am sure that a lot of things
are Ben Franklin's fault, but I think we have ample evidence to
indicate that this is not a burden exclusive to the American people
nor nonexistent prior to the middle of the 18th century.

Frde, your solution would solve the problem, certainly; but it would
not explain it.  This is a puzzle for the intellect and not simply a
matter of practical housekeeping.

Tryx

@Archeo

Nice point that, the phenomenen may be widespread but only observable for 'pairs'.

However I was only partly joking, the rest was deadly serious.
Socks should always be kept well away from all other garments.

Segregating socks?  That would be politically incorrect, either by
depriving them of social contact with the greater community of dirty
and washing clothing, or by treating them as higher members of the
community  - regardless of how they feel about the matter.  The socks
are not responsible for this problem and should not be ostricized for
its occurrance.  Maybe the fitted sheets should be, as they seem to be
the culprits.  They can also be replaced by harmless plain sheets. 
Indeed, they are the newcomers to the community, foreign intruders. 
Of course, any regulations to eliminate them must allow them to be
phased out so that those which are now part of the community - despite
contention about their social intergration   -  can live out their
useful lives in peace.

I see some profound sentiments here, some searching thought, and some
strong conviction.  Where might this lead?  Why, entire philosophical
systems and maybe even religions have been founded on less.

Tryx