There is no reason for Facebook to go public anytime in the near future. It will be more and more revenue positive as it refines its advertising model. Zuckerberg's contribution is therefore worth very little at the moment, outside of the tremendous commitment it implies for Mark. At some point, he will probably control huge amounts of wealth and it's bold of him to sign away most of the cash before he ever has control over it.

But wouldn't it be amusing if Facebook were to go the way of preceding social networks, and leave the "world's youngest billionaire" looking a little silly for pledging a fortune that never materialized?