If Facebook committed 100 billion felonies (where each intercepted message is a felony,) and each would carry 5 years in prison if I did it, then there are 500 billion years in confinement to divide between the stock holders. If someone owns $1,024 of Facebook stock (which is one-one-billionth of the total) then that stick holder would be sentenced to 500 years in confinement in a just system.
We do not have a just system, but there are those if us who will fight for one.
Perhaps the boys and girls at fed.gov can move 0.0001% of the way towards justice by seizing Facebook, liquidating the company, and handing out any money that is left to the people whose accounts were spied on.
Of course all if this assumes that each and every employee or former employee or contractor at Facebook who knew about this never, ever gets out of confinement.