So, assume I already left the company and exercised a big bag of common options and so I have a decent amount of common shares. If they tell me to sign something that looks shady I just say: "No, it looks shady".
What then, can they do?
It doesn't take a lot of imagination to see that this can happen. People are generally naive, and there are just a few that will resist and fight.
I am not naive enough to believe it would work, as they would probably find a way to screw me regardless, but my stance would be firm.
After my experience with startups I have become completely intolerant to corporate greed and injustice, so these days I am purely in a business transaction with my employer and I know exactly what to expect and when to expect it (which is why I get paid in RSUs rather than stock options). I like to think I wouldn't fall prey to this sort of petty begging.
* Access to decision makers
* Greenfielding a product
* Excitement / fast pace
* Novelty
* Great learning experience before launching your own venture
It's not for everyone, but I've interviewed dozens of developers who only want to work at startups for these reasons.
And for founders, obviously there's the upside of owning a business, the status of being funded, the ability to be your own boss and the potential for massive impact and wealth.