Nope, I can't take it seriously either. It has too many connotations of laziness, miseducation, stupidity and even selfishness. When it's used in the worst way possible ("I wanna to see u." / "I wanna a friend." / "Who wanna meet me?")... well, that's when my eyes burn and my soul rots.

It is my understanding that while it is not a word it is being allowed in writing in situations were someone is talking to give just the way it was said.

Don't go there Kevin - Abandon hope all ye who enter here! Where ya gonna stop, huh?

Girls just wanna have fun Kev, so watcha gonna do about it?

I believe it is widely used in spocken language. Even so i would not use it in writting.