The basic premise is one that I'm surprised no one's done before (as many great ideas are, really): LFGBlizzCon is a site for coordinating meetups and other activities during the con. Shelbi describes it as a "simplified social networking site dedicated to those of us who plan on attending BlizzCon this year. I wanted to create this site so we can all get to know each other online and then meet up at the con." To be honest, while I can see how that would work, it also seems to me it would be useful for people who already know each other as an easy-to-use, one-stop coordinator for how they plan to hang out during the convention.
Either way, it's a neat idea and good people behind it, so go give it a look-see.