It often is seen over other messaging programs, and it also is seen on internet message boards, much to the chagrin of readers who dislike the laziness associated with not typing the additional characters in longer posts, as the text becomes impossible to read.
typical AOL speak: lmao, ha funi shit, u be sey rofl cnt fukn get over dat... omfg wtf my fukn tech wnt nw? she a bitch! wll gtg, ttyl, brb, l8rz!
(Do not confuse with the more structured and less annoying L33Tspeak)
Example: "OMG I M SO FCKIG AWSUM!!!!!1 CUM WURSHP MEE BCH!!!!!1"
"Dude, don't use AOL speak..."