Rather than open this with some silly “OMG did u hear bout LOL going into OED,” or anything else of that sort that will have me dying a little inside, I’ll just come out and say it in as blunt a manner as I can: “OMG” and “LOL” are now in the Oxford English Dictionary.
For the March 2011 release of OED Online, we have selected for publication a number of noteworthy initialisms—abbreviations consisting of the initial letters of a name or expression. Some of these—such as OMG [OMG int. (and n.) and adj.]: ‘Oh my God’ (or sometimes ‘gosh’, ‘goodness’, etc.) and LOL [LOL int. and n./2]: ‘laughing out loud’—are strongly associated with the language of electronic communications (email, texting, social networks, blogs, and so on). They join other entries of this sort: IMHO (‘in my humble opinion’) [IMHO at I n./1], TMI (‘too much information’) [TMI at T n.], and BFF (‘best friends forever’) [BFF at B n.], among others.
I blame you, Internet.