He has more impact and reach at Facebook than being the US President, me thinks.
Does it matter? I can't see the Democratic Party nominating him. And after 2016 it will be a while before the Republican Party thinks that the rich business guy is a good idea.
He negotiated an exception where he would retain voting rights in facebook in case he took a leave of absence to run/serve in office. Hmmmm....
I'd vote for him. He'd help pass so many people-friendly laws that undoing his reforms would take decades. :)