I expected the majority of people to say they lack a co-founder, not an idea. Ideas are pretty easy to come by from my experience. Finding someone who compliments your skill set, is ready to go "all in" with you, and you actually click with is a much more difficult task.

For anyone who is looking for an idea, is a hacker, and lives in SF - I have an idea for a startup and am looking for a cofounder. Email me (in my profile) for more information. I am looking for someone who is interested in virtual goods/currency and the free-to-play gaming model.