Still think Facebook applications are just novelty widgets with no intrinsic value? Think again. A developer has just sold on eBay his Logbook application (pictured), which lets people catalogue their music, films and books and make money from Amazon sales.

The winning bid was £2,550, which doesn’t sound like much until you have a look at the application’s page on Facebook, and see it’s only got seven active users. That’s $364 per user, in other words.