Facebook’s new Messages product is built on the new hBase storage system, and will therefore require a new set of Messages APIs. There won’t be added functionality in the APIs, though, and they aren’t designed to give developers new channels for communicating with users. A beta of the new read-only API will be available to registered developer accounts, but developers with existing applications can still call the old APIs until the new Messages product is rolled out to all users.
The read Graph API and FQL let applications which receive permission from a user to access their inbox. The APIs could be used to build desktop inbox readers, or mash a user’s Messages history with other data to create message maps, rich content timelines, or provide statistics on who a user messages with.
To preserve the privacy of a user’s inbox, applications won’t be able to message users at their @facebook.com email address, which can easily be determined from a user’s vanity URL or user ID. This creates a layer of protection which can be penetrated by a user’s friends and other humans, but not by applications looking to send unsolicited email.
The new Messages product works with the Jabber and XMPP instant messaging standards, so all existing apps which integrate with Facebook Chat will function normally.
Facebook is considering creating additional APIs to give applications more granular inbox access and control. The company is looking to gather more information on what developers would be interested in using before making a decision.