Shorthand typing. Fair enough, if you're under the age of 15, but most people tend to grow out of it by then. And I suppose it's ok if you're texting.
But not if it's online and shit.
I don't mind a bit of, "hey, how r u?" That's kinda acceptable.
But the whole, "o hya, hwr u, wht u bn up 2 2dy?"