I think that's just ridiculous. I don't even like it when people go to the extreme when using abbreviations... Not just "lol" and "brb". Those are fine, but when you have to sit and decipher the sentence? A friend of mine (who is younger than I am) refuses to type properly. A typical conversation with her:
lol n then i wnt 2 the store aftr right, n all thse ppl were thr doign their xmas shopping lol iwas like wtf.
WTF is right.
I think their implication that it's only being used by teens refer to the extemes I mentioned. I don't know many people who are older that shorten everything to the point where it's almost illegible. When I first went online, in about... 1999, or so, I mostly went into chatrooms (back when MSN chats were free). Practically everyone used shortforms. I did too, until I started posting on messageboards, and realized how ridiculous things in short form looked in an actual post. On IM and in chats, you sometimes have to respond quickly, which is why there are all of these slang words, and shortened versions of thiings, but on a forum, you can take the time to type things properly and with good grammar. I get annoyed when people (not necessarily here) post stuff like that. You have enough time to type things properly... It's not as if you're in a rush, so why not just do it?
Anyway. When it comes to actually saying those things out loud, I think it'd be a little weird. Occasionally, I'll be like, "Oh em gee!", but more in a mocking manner than anything.