Startups in my portfolio at CRV (we're the guys that funded Twitter, Yammer, Millennial Media...) have plenty of cash and I think you'll make more money working in a startup and enjoy life more.
There is no risk, because if the startup fails, you move to the next one. Silicon Valley is like working in a big company with multiple divisions: you may change 'departments', but you're still working for something where everything loosely aligns as the same goal.