But in this case the Facebook board (which has a fiduciary duty to the company, not to Zuck) paid $5B when the BATNA had them pay $100M. The extra money bought the company nothing; the only benefits were to Zuck and Sandberg personally, which makes the $4.9B undeclared income -- if they didn't disclose it as part of their compensation on the relevant SEC documents and W2s, it's tax and securities fraud. And hence this lawsuit.