What exactly are you implying, he should have blackmailed them?
I can see that he's successful, but there are so many ways he could have played this better. Let's compare:
A. A lifelong agreement from one of the most successful people in our generation to give a positive reference and introductions to top investors, in exchange for a small concession (non-disparagement and non-litigation regarding the company and the termination).
B. Emotional catharsis associated with discussing a termination in embarrassing detail.
I'd take A.
All he needed to say was, "look man, I'm sorry we got off to a bad start. Let's talk about how we can help each other out in the future."
Mark Zuckerberg has a bad reputation? On what planet do you live? A lot of people dislike him, sure, as a lot of people will dislike any billionaire, but he's the most successful person in our generation... and it's pretty evident to me (and to most) that at least some of that is earned.
Large companies have deep pockets and don't want information to get out. He couldn't have gotten $100 million out of this, but at the time, he could have definitely had the cliff voided (which would have been enough to get him comfortable)... but now it's far past too late. If nothing else, he could have let the cash and stock go and settled on a glowing reference from Zuck himself-- which would have made his career. There are so many ways he could have turned this to his career benefit.