Add another former Googler to the Facebook ranks. Just recently, Facebook hired Greg Badros, formerly a senior director of engineering at Google, as a new director of engineering.

While at Google, Badros was responsible for AdSense, Gmail, Calendar, Reader, and Orkut (Google’s social network that’s most popular in Brazil and India) at various points over the last six years. Prior to Google, Badros was the Chief Architect at InfoSpace. He will report to Facebook’s VP of Engineering Mike Scroepfer, who joined the company from Mozilla (at the time as a director of engineering) last summer.

Badros’s deep experience managing the AdSense engineering team over a period of three years could come in handy as Facebook starts to monetize Facebook Connect. Facebook CEO Mark Zuckerberg told us recently that the idea has always been that most of the action on the Facebook Platform would happen off of Facebook.com proper, and Badros has experience building systems flexible and scalable enough to serve a wide variety of publisher partners.

Badros’s experience managing Google’s Gmail engineering efforts over the last two years could also come in handy as Facebook continues to build out its messaging infrastructure. Just last week, Facebook announced some updates to the Facebook Inbox to decrease clutter, but with the launch of Facebook usernames we could see new kinds of messaging emerging in Facebook in the coming years that would require different architectures to work well over time than Facebook’s existing channels do.

It’s another significant engineering hire for Facebook. The company is still searching for someone to head their payments efforts as well.