I have worked at three startups where I joined at <10 employees. Best result was stock-options worth less than the price. Worst was they owed me a paycheck. I had fun, and we had a good chance of making it big with all of them. I like to think that if I'd been offered the chance to join Google at <10 that I'd have been wise enough to spot the potential value of the company and take more stock. Unfortunately: a) I was not asked and b) I probably would not have had that wisdom. However, if I had been asked, but had not taken more stock, I'd still be a millionaire, just not a billionaire.