Because if you're going to a convention about a game, you might as well turn it into a game, right? Just for fun, we've put together a BlizzCon Bingo card-- save the image, print it out, bring it to BlizzCon, and then make a mark whenever you see something at the convention on the card. There's all kinds of things on there, everything from a Northrend expansion, to someone saying "kek" in RL, to Blizzard CMs and developers.
All you have to do is observe five occurences in a row throughout the weekend, and you win! What, you ask, do you win? The satisfaction of a full and fulfilling BlizzCon weekend. I don't know about you, but if I leave Anaheim having seen a new Diablo, new midlevel content, or just a really quality Murloc costume, my weekend will be made.
And while lots of these are easy to recreate yourself (anyone can complain about their class), remember: no cheating! You must observe what happens, not cause it in any way. Good luck!