As I've said before, we have a rule in our guild prohibiting leet speak and excessive abbreviation in guild chat. That being said, I've thought a lot about the use of abbreviations in WoW and how they are affecting the language.
This might come from my days as an English teacher, but I think of the language as a fluid, breathing thing. The formality that people used when speaking 100 years ago doesn't exist now, and I doubt we would ever hear in game "pardon me, good sir, could you wait a moment?" instead of "one sec AFK" unless we were on an RP server or feeling particularly silly.