I have no idea why people still use it for entire sentances... Every once in a while, I'll say a word or two in '1337' speak just to annoy my friend, but when people actually write in it, it's just annoying. It seems like the only people who really use it anymore (by use I mean as a completely alternate form of writing) are 12-year-olds who still think that it's "cool". My cousin types like that on AIM... I refuse to talk to him until he starts typing in real English.
Along the same lines, check out this link, it's Romeo and Juliet translated into "1337" so the younger generations can understand this classic literature. It's pretty funny, actually.
http://people.cornell.edu/pages/slp29/romjul.html