To get and keep talent you need not just a good work environment but cold, hard cash. Paying employees with stock options and grants on a stock on the way up is a very efficient way to encourage people to work for you or to stay working for you. You can also pay people with actual cash, but that's significantly more expensive to match the same level of reward. People who worked through the elbow at Microsoft, Google, Amazon, etc. became millionaires. And there are plenty more elbows out there for the taking in silicon valley, in new york, and elsewhere. It can be hard to compete for and retain employees who are talented enough to earn their millions by seeking out some other company. This is a huge problem at Microsoft, for example, where the stock has been flat for a decade.

Certainly there are many good reasons to work at facebook, but how many of those reasons can make up for missing out on millions of dollars? This is all the more relevant right now because so many of the early employees have gotten their millions through the IPO, and that has all the makings of creating a cultural divide in the company between those who got theirs and those who haven't, and won't.