If you push people hard enough...

... they will either:

- not be as productive (obvious)

- start being deceptive about what they're actually doing (to avoid repercussions)

- finally, they'll leave for greener pastures

I realize you're coming at it from a personal perspective... but it's something for startup founders to keep in mind as they bring on employees / non-founders.

There's a great example of this happening in practice in this video: http://www.youtube.com/watch?v=zuJU1dzc5kM