Another pet peeve. Rebus disease is the evil habit of using letters and symbols for words in written conversation, after the manner of a rebus.
This is not a problem with acronyms like "ROTFL" or "RTFM" that are legitimate abbreviations. This is not a problem with smileys which don't stand for written words per se.
I mean the kind of people who have some kind of perverse aversion to words like "for" and "you" and "are", and usually proper spelling and punctuation as well. Examples:
"how r u 2day?"
Translation: "How are you today?"
"ur writeup suks"
Trans: "Your writeup sucks."
"will u do that 4 me 2?"
Trans: "Will you do this for me, too?"
Habitual offenders: Prince, the stereotypical teenage girl on AOL, and an alarmingly high percent of my friends-of-a-friend.
Update, Nov 4 2K:
I have just witnessed my first international sighting of rebus disease. A 14-year-old girl from .mx with the word "salu2" in her profile.
I feel ill...