Facebook has only acquired three companies in its history, that we know of: Parakey, FriendFeed and Octazen. Facebook bought Parakey in 2007, FriendFeed last summer, and Octazen in February. And now it’s snapped up a fourth, a small photo sharing service called Divvyshot.

The Divvyshot team will be working on Facebook’s in-house Photos app, the company announced on its site today. Facebook itself isn’t saying much, besides this:

We recently completed a small talent acquisition involving the team at Divvyshot. We’ve admired the engineering team’s efforts for some time now and this is part of our ongoing effort to add strong talent to help drive the company forward in its efforts to be the central way for people to connect and share information.

Divvyshot’s team will begin Facebook’s engineering training ”Bootcamp” on April 12th. Terms were not disclosed.

More than 3 billion photos are uploaded to Facebook every month, according to its self-reported stats. It’s the largest photo-sharing service in the world. But the product has stayed pretty basic over the years, although it has recently been making some upgrades, like a new photo uploader.

Divvyshot, as the name suggests, has focused on making group photo sharing easier; it only had around 40,000 users, and had raised a small amount of funding from Y Combinator. Its service lets you easily let lots of people reshare the same photo, or add to photo sets, and upload in bulk from other services. On that last feature, we could see Facebook wanting to make it easier for users to import lots more photos from other sites, as that means more content for their friends to look at on the service.

But for the companies aren’t saying more about their plans.

The move could also signal Facebook’s increasing investment in its core products. FriendFeed specialized in developing news feed features and an open platform, the news feed and platform are arguably Facebook’s most important features, and today the FriendFeed team holds leadership positions in engineering and product roles working in those areas. Octazen gained a reputation among developers around the world for figuring out ways access and share user data across the web, and now the team is working on Facebook’s contact importer, from our understanding.

Perhaps we’ll see more talent acquisitions designed around improving specific core Facebook products?