I received an email from a young man thanking me for a graduation
gift.  Is it bad etiquette, or are email thank you letters now
acceptable versus hand-written correspondence?  What would the high
school Miss Manners say?

Hi faith2005,

I don't know about the high school Miss Manners, but the real Miss
Manners has been quoted as saying "E-mail can be used for light
favors, but it does not replace the serious note of thanks."

http://www.zaner-bloser.com/html/ChicagoTri_2000.html

Researchers at Ask Yahoo! consulted various sources and came to the
same conclusion.

http://ask.yahoo.com/ask/20030523.html

However, you might also consider platonist1's defense in the comments
below.  It is likely that the young man was not aware of this
etiquette standard and was simply using a medium of communication that
was usual and customary for him.

--efn

I found the Yahoo link most helpful.  Thanks.

You spent the time to go out and buy this person a gift. The least
they can do in return is to mail (yes, I mean snail mail)a letter or
card of appreciation. In fact, when most high school students purchase
their graduation announcements they are given the option of purchasing
matching thank you notes which implies that they should send notes.

Hi,
It was kind of you to send a graduation present: I didn't get any,
which may just be a british thing. Anyway, I think it is important to
understand that for someone who has just graduated, it is likely that
vast bulk of their written communications are by email, and email
probably means as much to them as pen and paper ever meant to you.
His/her gratitude is no less real, I am sure. If you are a close
relative, friend, or family-friend, I would take it as a sign that the
new graduate feels on sufficiently good terms with you to dispense
with what many consider to be superfluous and outdated customs.
Don't worry about it.