They do not approve the price, but they have to approve the transaction and it can only take place within one of the allowed trading windows (Facebook has non-t

They do not approve the price, but they have to approve the transaction and it can only take place within one of the allowed trading windows (Facebook has non-trading periods leading up to major events to prevent insider trading). They also have to make sure that they remain within the 500-shareholder rule, which would otherwise force them to go public (which is what happen to Google).