At some point during E3, this happened, but we were far too busy working to see it.
I've always wanted to see a flash mob in action, even if it is just a marketing tie-in. It seems I've missed my chance. From the YouTube description:
Attendees at E3 2010 were surprised with an Alien Invasion Flash Mob to celebrate the release of the new TOY STORY 3 video game. Over 100 fans came together and danced to music and choreography inspired by the game on the opening day of E3 at the LA Convention Center.
Opening day? Let's see, that puts me at the Sony press conference, cursing at the internet and tapping away at my netbook's tiny keyboard. Not a fair trade, methinks.