In the worst-kept-secret department, location-based mobile service Gowalla confirmed that it has been acquired by Facebook.

According to a blog post by Gowalla Co-Founder and Chief Executive Officer Josh Williams, Gowalla’s user data is not part of the transaction, and the Gowalla service will be terminated by the end of January, although users will be able to save their data and photos.

Williams did not discuss what role he and the rest of the Gowalla team would play once they joined Facebook, but it has been widely reported that they will work on the impending timeline profile.

According to sister blog Inside Facebook, Facebook did not specify how many Gowalla employees it would add, nor what they would work on.

Terms of the transaction were not disclosed, but the valuation for Gowalla is roughly $28.4 million.

Facebook released the following statement to us via email:

We’re excited to confirm that Gowalla co-founders Josh Williams and Scott Raymond, along with other members of the Gowalla team, are moving to Facebook in January to join our design and engineering teams. In talking with the Gowalla team, we realized that we share many of the same goals: building great products that reach millions of people, making a big impact quickly, and creating new ways for people to connect and share what’s going on in their lives. While Facebook isn’t acquiring the Gowalla service or technology, we’re sure that the inspiration behind Gowalla will make its way into Facebook over time.

And Williams wrote in his blog post:

About two months ago, my co-founder Scott and I attended f8. We were blown away by Facebook’s new developments. A few weeks later, Facebook called, and it became clear that the way for our team to have the biggest impact was to work together. So we’re excited to announce that we’ll be making the journey to California to join Facebook!

Gowalla, as a service, will be winding down at the end of January. We plan to provide an easy way to export your Passport data, your Stamp and Pin data (along with your legacy Item data), and your photos, as well. Facebook is not acquiring Gowalla’s user data.1

We know how much many of you loved Gowalla. It’s been the highlight of our lives as we’ve built it with your help over the past two years. As we move forward, we hope some of the inspiration behind Gowalla — a fun and beautiful way to share your journey on the go — will live on at Facebook.