Retards who are too lazy to type four letter words.
Or, use 1337 speak or warez. It just makes them look idiots. Especially when they talk like they're on AOL when they are on message boards. It's not legible. No one wants to read their crap. Usually, illiterates try to diss you in school. Just bring up their poor english and use it against them.
Illiterates should be killed.