Please settle a friendly disagreement:  Which of the following two
sentences are correct? Are either of the sentences incorrect?
1.) Data in its original format is subject to manipulation.
2.) Data in their original format are subject to manipulation.

Hi sibilance:

Thanks for the interesting question. As a part-time technical
writer/editor, this question has bothered me for many years.

The short answer - both are acceptible English. But, if there's money
riding on this, I'd say that the second, plural version is "more"
correct. (Yes, yes all you commentors, I know that there's no such
this as "more" correct.)

Here are some data to back up this claim:

AskOxford - Is 'data' singular or plural?
URL: http://www.askoxford.com/asktheexperts/faq/aboutgrammar/data
Quote: "Strictly speaking, data is the plural of datum, and should be
used with a plural verb (like facts). However, there has been a
growing tendency to use it as an equivalent to the uncountable noun
information, followed by a singular verb. This is now regarded as
generally acceptable in American use, and in the context of
information technology. The traditional usage is still preferable, at
least in Britain, but it may soon become a lost cause."

Dictionary.com - data
URL: http://dictionary.reference.com/search?q=data
Quote: "da·ta...pl.n. (used with a sing. or pl. verb)...Plural of datum."

Search Strategy (on Google):
* data "singular or plural" 

I hope this helps!

websearcher

Websearcher is right and the quote from AskOxford explains it
succinctly---both senses of "data" are acceptable (as long as you
don't juxtapose them awkwardly). Some grammatical proscriptionists
insist that the noncount-noun sense of "data" is "wrong" because the
noun originally had only a count sense (datum sg./data pl.). But the
fact is that it's a normal process in living languages for words to
grow new part-of-speech senses over time. Sometimes the new growths
survive; sometimes they don't. In the case of the count-noun sense of
"data," the new growth definitely survived and thrived. People who
"hate" such change tend to be monolingual and therefore tend not to
understand that languages are in reality only stable-but-dynamic code
conventions.

Sorry, that should read "In the case of the noncount-noun sense..."

IndexTurret - who are you?  I noticed that you comment on many
questions, but do not ask any ... that's a bit odd.

Could indexturret-ga be like me and not own a credit card?

Regarding folks who comment but don't post questions, I used to be one
of those folks. Before I became a Google Answers Researcher, I posted
several hundred comments on GA, but I posted no questions. Later, as a
GAR, I asked a few questions, but my early career here consisted
solely of comments. There are many prolific commenters who have not
posted questions.

If you replace "data" with something like "figures" or "numbers" it
shows which form is correct or, as someone else put it, "more
correct".

It's become a matter of house style.  As a professional editor, I edit
to house style, regardless of personal preference.  Technical
publishers typically specify "data is";, more traditional publishers
such as of textbooks may still call for "data are."  When it comes to
grammar, I am more traditionalist than otherwise, so I treat it as a
plural noun myself.  I wouldn't call it a lost cause because I
wouldn't call it a cause; but I would certainly call it a practice
that is rapidly becoming obsolete.

Whichever way you treat it, treat it the same way throughout a
document, manuscript, article, series, or site, and don't mix
interpretations.  Never mind "don't juxtapose them awkwardly"; don't
use it differently anywhere within the documentation system in which
it occurs.  Either use is justifiable and defensible if done
consistently.

Archae0pteryx

Hi websearcher-ga, pinkfreud-ga, archae0pteryx-ga, et al.,

On a website from Australia (the one for finding the nearest public
WC), another alternative is used:  "datums".  A quick search suggests
that this usage is rampant, accepted, whatever in the field of
geometrics, but maybe in a special meaning, say, the pair of Lat./long
figures.
Anyway, 
Cheers!