First, I really wouldn't say Facebook was a big idea when it started. It was about getting Harvard students laid, with some long-shot plans about connecting the world together gradually over time. I could come up with some half-baked paths that a few of my ideas may follow to become a huge company, but of course that is more about luck down the road. I like to focus on ideas that can solve a problem right now and make money.

Second, risk is not a binary concept. You have an efficient frontier of risk/reward points and you simply choose your spot along that line. If you want to start the next Facebook, you might be looking at 1,000 competitors. If you want to build a Settlers of Catan clone, it's more like 3. There's still risk, but it's greatly reduced, and with that reduction comes a reduction of potential return. Feel free to swing for the fences-- but every team needs guys who can get singles and RBIs, not just home runs.

Happy to hear some examples of ideas that you think have sufficient potential and charm. :)