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.
