The latter half of your comment reveals Zynga's deceit in pulling this, and why it's not just another case of grudgingly correct capitalism. Zynga used the promise of unvested shares as motivation for its workers. Taking it away now is akin to promising delicious, gourmet cheese to a mouse while it runs on a wheel for a few years, then saying, "Hey, thanks, but a renewed evaluation of your performance indicates you're more deserving of some more bread crumbs every year, no cheese." You can't reneg on valuation made during the early stage.