This seems slightly fishy. How can an event that's just announced claim to have 300 people coming?
The fire marshall comes in handy there. "Max Occupancy: 301 persons"
That's probably what I'd do -- "hey, how much space we got?"
I work in the Plug-n-Play Tech Center and I haven't heard of this yet. That could just be because it's 2 months away and I'm not on the mailing list, though.
My reasoning for it not being fishy is that it's part of Community Next so it's not just some random event. Noah Kagan/Andrew Chen have been planning this for a long time, flying out top 100 FaceBook devs etc. > http://flickr.com/search/?q=communitynext&z=t&s=int
We are expecting to have around 300 people attend.