Font question

Brishen forwarded me the following question, that I’m hopeful one of you web and/or designer types might have an answer for:

Hey guys,

I’m writing to all of you since you know something about the subject, and i’m looking for answers.

i’m having a debate with [a guy at my work] about the reason why sans-serif fonts have become the unofficial standard for type on the web. the reigning logic is just that “it’s easier to read on screen” whereas serif faces are easier to read in print. i need to know if there’s any backup for this argument. he says it’s just subjective aesthetics. i say it has something to do physiologically/perceptually with the way your eye processes backlit images versions reflected-light images (i.e.in print). i have heard this a million times but don’t know of any real studies on this specifically or even where this theory even comes from.

so, would any of you know of any litterature with some real supporting information in it? either for or against would be good, i’m flexible about it. a million thanks if you do.

let me know,