The crazy thing to me is: 1) the fact that employees are granted options instead of shares is an artifact of tax law, and 2) the fact that there's a 90 day exercise window is also an artifact of tax law. Yet, companies constantly come up with post-hoc justifications of why only giving a 90 day window is fair. There is big resistance to change on this point. Even Ben Horowitz and Sam Altman don't think it's a clear decision! http://genius.com/B-horowitz-lecture-15-how-to-manage-annota...

If you were to derive how to think about employee ownership of a company as a form of compensation from first principles, you'd never come up with options and you'd never come up with a 90-day exercise window on top of that. Those are both artifacts from tax law yet it's become the standard form of compensation!