Not if he negotiated properly coming in, which I suspect he did given this quote: “I had always been upfront with Mark that I eventually wanted to do another st

Not if he negotiated properly coming in, which I suspect he did given this quote: “I had always been upfront with Mark that I eventually wanted to do another start-up.” If he was upfront, then that means before he came on board. He probably negotiated a condition that if he stayed through the IPO that xyz would happen (vesting, whatever else). He carried out his end of the deal, therefore xyz happend. Everybody wins (except those who bought FB on the IPO (or on one of its first 12 days as a public company).