“Value” of a Twitter or Facebook follower

Is a Twitter user worth 10 cents a month; a Facebook user, $2.75 a year?

As reported by the BBC, USocial, an Australian company, is "offering a paid service that finds followers." 

The estimate for a Facebook user comes from a comment from Jonathan W on a Silicon Alley Insider story that reports Facebook's annual revenue at $550 million.  If Facebook has about 200 million members, it works out to $2.75 – a year.

You can quibble with the methodologies, but to me the message is clear:  Social media objectives should be focused on building communities, not revenue.