There’s well over 10 billion photos on Facebook, making it the largest photo-sharing site on the web. Now that’s a lot of people tagging each other. Face.com’s Facebook app, called Photo Finder, has taken on the task of tagging every last one of these photos, and a month after launching its beta version, Photo Finder has scanned over 400 million photos, getting through 13 million photos in a single day.

The purpose of all this scanning? To tag your beautiful mug. We covered Photo Finder’s launch on the Facebook application platform a few weeks back, and I noted how well it worked for tagging all sorts of photos of myself. The timing was perfect, because I’d just returned from my trip to SXSW, which added nearly 200 photos that had been tagged with my name. The photos came from several different albums, including those who I hadn’t added as a friend yet on Facebook.

The convenience of having an application tag the photos of me introduced the potential for a time-saving tool that just about any avid Facebook user can appreciate. Some other useful aspects of the Photo Finder application include the ability to organize photos accordingly, as well as discover new people that are in the peripherals of your Facebook social graph.

So it appears that the Photo Finder application for Facebook has brought additional success to Face.com, the company with facial recognition technology behind the Photo Finder application. It’s not too often that you hear of such success stories on Facebook anymore, as many companies that once would start out with a Facebook application in order to save time and money, or turn to Facebook apps in order to grow their existing service now deal with the fact that a good deal of Facebook’s platform activity has plateaued. But Photo Finder’s integrated approach to tagging photos provides value, and fits well with the Facebook experience we already know, love, and for which we return to Facebook on an hourly basis.

Face.com is likely looking to grow its company by seeking other platforms for which its technology could be directly applied, but the majority of its application success is likely to remain on Facebook for some time.