If you had clear reasoning that you was dismissed for a reason other than failure to perform duties, then you would have cause to sue.
FTA two people already retained council, settled and still got to keep a portion of their stock.
What Zynga is worried about is that if they're going to be publicly valued at $1 billion, the guy who owns 5% of stock because he was there from day one is going to land $50 million and walk.
I imagine that the biggest problem with IPO's for companies like Zynga (especially if they're acting douche to their employees) is that they risk losing a lot of employees. Either selling up stock to get the cash, or simply retiring to live off dividends and slow-stock sale tactics.
> [...] Kmart’s discharge was in 'bad faith' and that, even without a contract, such a termination gave rise to tort liability. The court agreed [...]