A question about vesting
brk: I am unclear if you are talking about bona-fide stock, or options.If you have a stock grant with a vesting schedule, the vested shares become YOURS and are irrevocable, like pay. (and yes, I am speaking in the TYPICAL sense here, there are 1000 sub-possibilities).If you have stock options, then as they vest you earn the right to purchase those shares at the strike price.  If you buy them, they are yours.  If you do not, those shares go back into the employee pool for potential re-allocation.And I don't know if you have a specific case in mind, but if you have some "company" and one "cofounder" drops out, it's rather unlikely someone is going to come along and purchase anything for any price.If your company is a real entity and was put together with even so little as templated "Let's Start a Company" kit from Staples, the specifics of this are likely covered in some manner in the incorporation docs.