How many employees does Facebook have? If they have around 5000 employees, then on an average, if they go public for the valuation claimed, every employee gets around $3M!
Given dilution, and grants etc, i'm gonna guess that 2000 employees will get 750k (a new house) and 500 (the first 500) will get an average of $26.25m apiece.
Though, i'm sure it's more logarithmic than that...
Warning: the following will make me look jealous and bitter, but so be it:
That the early employees get a giant pay-day is deserved, but the later you join, the less influential in the overall success you are, in addition to the fact that you're not taking any risks, like you would in an early startup. It seems that joining Facebook a year ago as a developer wouldn't be much different than joining Google or Microsoft in terms of benefits, salary, perks, responsibilities…
I guess I can only blame myself for not working at the right companies, or not making myself marketable enough to be hired at these companies, but I've never had a job that ended up with a bonus in the $500k-$1M range.