In summary:

- Become better at advertising

- Sell completely unrelated crap (water, gear, hardware, phone), because they've got a good brand and advertising platform

- Charge users and developers, "somehow" (great advise, thank you!)

- Sell their data (anonymously, though)

- Advertise more (pretty contrary to the claim that they have a brilliant, under-utilized advertising platform)

- Be something else (corporate intranet, dev. payment platform, eBay, Skype, Second Life (WTF?!), Online bank, cloud storage, Tor network, physical loyalty card)

Basically: There is no Facebook business model, besides the one they already figured out (advertising) and can't make work, and the one about selling their data, that users had a strong antipathy of (beacon).

Becoming a corporate intranet is a little viable, but it doesn't really leverage the Facebook network. A corporate intranet doesn't need the network effect that is really the cores of Facebook. They have Active Directory.

The most obvious way to monetise facebook is to me some kind of job advertising platform. They have all this data on people, like whether they're students, where and studying what, etc. Companies looking to recruit could buy job ad placements based on those criteria. (e.g. show this job to final-year CompSci BSc students at Cambridge and Oxford) The more specific and popular, the more expensive.

I suppose it's possible that they've explored it but there isn't a market for this. I guess with the job market right now might not be the best time for that kind of feature - on the other hand there are probably lots of users who would use it.

Several of the suggestions are very low-margin activities; Facebook might not be able to earn serious money from those even with improbably huge revenues. But Facebook does have a capacity to gather an astounding amount of data about each user, and it would be missing an opportunity not to find some way to monetize that. The downside risk, of course, is that if Facebook finds a way to get money from users' willingness to share personal information that they may become less willing. Online social networks appear to have huge elasticity of participation depending on how the business model and thus culture of the nework changes.