Facebook appears set to launch a social check-in Deals feature, according to an email forwarded by a participating retailer to Facebook watch-dog blog All Facebook tonight.

The email says that this particular deal will give Facebook users a free item when they tag three of their friends as present at the retailer's location. Facebook plus Groupon? Considering how much profile and social data a Facebook Places check-in can carry as a payload, this sounds a whole lot more valuable to retailers than a Groupon deal. This is very different than the kind of Places-powered hyperlocal advertising that most observers were expecting to monetize the Places feature.

This will no doubt make Facebook Places more appealing to users as well. As Nick O'Neil writes at All Facebook, "One of the major criticisms of many of the existing check-in services (Foursquare, Gowalla, and even Facebook) is the lack of incentives for checking in to various locations."

What's to stop people from tagging friends who aren't really there? In theory, even if a person was falsely tagged as present at a place - they would still receive a word of mouth promotion of the place as a result of being tagged.

The Data Power of Facebook Deals

Many observers expected Facebook Places to be combined with a system of hyper-local advertising. This is different; it looks more like the Groupon hybrid of commerce and advertising, lowball commerce as advertising. Picture Groupon type commerce with a rich layer of profile and social data powered by Facebook on top, though. It's one thing to get piles of people coming through your door for deals, it's another to know all about them and their friends.

Foursquare says retailers like the detailed analytics that it provides retailers, but Foursquare doesn't have nearly the same level of profile detail on its users as Facebook does. Almost no company does. Would you share selected parts of your Facebook profile with the local brewery in exchange for a free round of beer? Many of us will.

How much profile and social data would retailers be given access to, and in what form? Such are the mysteries we can only ponder while the program remains a mystery.

Groupon, a startup that's being called the fastest growing startup in history, isn't standing still either. It's now releasing a self-serve feature for businesses. Facebook Places Deals looks self-serve at the outset, though.

Is the email O'Neil posted a redacted copy of for real? In all likelihood it is, though we've received no response from Facebook yet after requesting comment by email. Update: A Facebook spokesperson replied to our email saying only: "As a matter of policy, we don't comment on speculation. We have nothing to share at this time."