OMG! We can't accuse our BFF Oxford English Dictionary with being behind the times anymore. The OED has finally managed to get with the program (LOL!):
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.