Found via Kottke, this Wired article covers "The Secret Cause of Flame Wars". Actually, not such a secret -- anyone who deals with email constantly, and in delicate situations, knows that it's much to easy to be misinterpreted.

The researchers took 30 pairs of undergraduate students and gave each one a list of 20 statements about topics like campus food or the weather. Assuming either a serious or sarcastic tone, one member of each pair e-mailed the statements to his or her partner. The partners then guessed the intended tone and indicated how confident they were in their answers.

Those who sent the messages predicted that nearly 80 percent of the time their partners would correctly interpret the tone. In fact the recipients got it right just over 50 percent of the time.

Nice to put some research and numbers behind it. It's interesting that the study focuses on email, and not instant messaging. It's easier, in the fragments of discussion that pass in IM, to get across details of expression...that plus the fact that I'm much more likely to toss in a smiley in IM whereas I won't in email.