There's a whole class of interesting, valuable challenges that you'll never get close to working on when you're alone and bootstrapping. Building value at a larger scale, as part of a larger team, can be equally fulfilling, as long as the team is great.

Also, while Google, Twitter and Facebook are great outcomes, there's a 1000:1 chance against your particular idea. It's 10:1 you'll be able to start it at all, then 10:1 you'll survive until funding/bootstrap, and then 10:1 you'll exit. If you want the best expected value (in dollars) for your time, go work for wall street firms!