Facebook’s IPO has been announced, and this means lots of details on Facebook financials have become public. The most interesting bits for social game developers (in VERY broad terms):

• Almost all revenue from Facebook Credits is generated by games.
• Zynga makes up 80% of the total Facebook Credits revenue.
• In broad numbers, on Facebook, Zynga has MAU equal to 1.5x all other game devs combined. But Zynga’s FB Credits revenue is 4x. That’s an idea of how much better Zynga is at getting players to pay.
• Most of Facebook’s revenues come form advertising.
• Facebook mobile gaming is in its infancy.
• Half of Facebook users use the site via mobile, and this percentage is growing very quickly, but Facebook does not monetize them with games nor advertising.

This means that the first game developers to jump on board for Facebook mobile gaming have half of the entire Facebook userbase all for themselves, and Facebook will be more than willing to help them succeed. This was reflected in Zynga’s shares soaring after this information became public – it turns out that Zynga’s dependence on Facebook is matched by Facebook’s dependence on Zynga.

Of course, the problems associated with Facebook mobile as a gaming platform are huge:

• Screen real estate on a mobile platform is extremely limited, there’s just not much room to show ads or games inside Facebook mobile without severely reducing the amount of actual content the user can see.
• Phones already have gaming (and app) and platform integrated
• On-the-fly game downloads and persistent server connections are a staple of desktop Facebook games, but on mobile the connections will be less reliable, much slower, and capped.

So, Facebook mobile gaming will be a very different beast from Facebook desktop gaming. Many lessons will carry over, but many established patterns like the neighbours bar, notification popups, crammed isometric views, and Flash programming will go away. The nature of social interactions, gameplay design and UI in Facebook mobile is still full of unknowns, and whoever solves it first has (for now) a big shot at a pretty large pot. The sooner you start, the better.