Facebook just announced an upcoming subscription payments service, giving developers another potential revenue stream beyond the sale of virtual goods.

This new feature will be available to to all Facebook.com and mobile web apps in July. In the meantime, you can get started by reviewing their documentation for more details. Subscriptions are already being tested by developers such as KIXEYE and Zynga.

KIXEYE's Backyard Monsters will start testing an offer of exclusive items for $9.95 per month.

This isn't the first time Facebook has experimented with game subscriptions. Last year, the Facebook Credits team told about a situation where a developer was using a subscription model and needed extra help implementing a recurring pay cycle. At the time, the team said the subscription model wasn't being used by studios in North America, but it was seeing some success in other territories.

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