Could it be because of the free stuff that they give out at the conference, or because of increased interest in developing with Google products?
justinsb's posterous has an interesting suggestion: Don't give anything away this year. For someone who couldn't afford the trip, I agree. Keep the scalpers out, and keep the developers in.
Announce that there will be nothing given away at Google I/O this year, offer free refunds to anyone that wants them, and open a waitlist. The scalpers will take their refunds, and the real developers will be able to get in.If the only reason that you want to go is for the free stuff, go talk to Oprah.
Google: Don't be Oprah. Be better than that. Help out the people that want to LEARN.