TagTile helps local businesses identify customers.

Facebook is amping up its mobile efforts, this time around commerce.

Facebook today bought a San Francisco-based startup called TagTile, a mobile-based customer loyalty business. Like Square, TagTile provides merchants with a free hardware device (see the white cube in the photo) for customers to tap on with their phone when they checkout. That, combined with the app, lets stores run coupon programs and offer loyalty rewards.

In a post on its site, TagTile said that Facebook is "acquiring substantially all of our assets." How much is that worth? Facebook isn't saying. But this acquisition clearly isn't Instagram and instead is typical of those that Facebook usually makes -- small deals to pick up the technology and the team.

The announcement also comes on a day when Facebook rolled out Facebook Offers, a way for small businesses to send promotions directly to Facebook news feeds.