F8 2011 Conference by Facebook
f8.facebook.com
f8.facebook.com
> just to watch Zuckerberg reveal something I won't use
I think you're overlooking the value. It's not about going for a keynote or being entertained/catered to; its about the interaction. The ability to talk to the people that've built the tools you are using is extremely powerful. Would you rather talk to an expert on a subject matter, or post a question on SO and hope someone has had a similar experience? This is just one of the reasons why conferences like this are "worth it".
Personally, I would rather that people post their questions - and then receive the answers - somewhere that's easily searchable, so that when other people have the same questions they can easily find an answer. There is certainly value in increasing the number of experts, though, so perhaps that's what you were pointing at.
$400 is that interesting price range where it will be a 'big waste of money' (as one other commenter put it) to anyone who isn't otherwise directly involved and profiting from the Facebook platform ecosystem.
$400 is simply an economic-based velvet rope.