For reasons that remain unknown - and are quite hard to guess at, for that matter - Facebook has split its private market stock. More specifically, the company announced this afternoon that it's conducting a 5-for-1 split.
If Facebook were going public, this would make it easier for the average investor to buy a share. But rumors indicate the per-share price is only around $80, anyway, and Peter Thiel pretty much promised just this week that Facebook won't go public before 2012.
Another theory, put forward to Reuters by a person supposedly familiar with the situation: "If you were going into Facebook, before they would have been able to say I'm going give you 10,000 restricted stock options, now they can say I'm going to give you 50,000; it sounds better. It's all optics."
Yet one has to assume that everybody capable of working at Facebook can multiply and divide, and is beyond such tricks as a result.
Feel free to leave you own theories in the comments section.