One study says so, but I'm not so sure. The study
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.
Okay, but the expectation of correctness is also based on what fraction of messages the viewer reads that are usually sarcastic. I wouldn't be surprised if the study selected sarcasm or the lack thereof on a 50/50 basis -- so, unless half of what's said on the Internet is said ironically, they're skewing their experiment. The proportion is almost certainly lower, especially since many people already realize that the Internet is not a great medium for communicating shades of meaning that we typically convey through tone of voice or timing. So while we're prone to misunderstanding each other online, it's not nearly this bad.