Via its new , Facebook will review applications according to several criteria, such as their trustworthiness, transparency and overall usefulness.

Developers must pay a US$375 fee to have an application reviewed. If earned, the certification is good for 12 months, after which developers must pay another $375 for their application to be reviewed again.

Games developer Christopher Bourton, co-founder of in London, worries that this might be the first step to eliminating the Facebook platform's traditionally free status.

"I do understand them wanting to cover costs, and trying to weed out the bad content and spamming Apps," he said via e-mail. "This won't achieve that. It will just prove who paid Facebook off."

"We are doing part of the work of verifying the App, and having to pay also. That just doesn't seem right at all," he added.