There have been some signals coming from Facebook that point to how it could one day become a platform for e-commerce beyond apps and virtual goods on Facebook itself. There are its patent holdings, and there is the code for a not live “Want” button to use on posts for particular products that could trigger a purchase. Today comes one more opening on this front, but from a third party rather than Facebook itself: couponing giant Valassis, which already works with some 15,000 advertisers to create electronic coupons, has launched a new Facebook app that lets brands offer coupons that can be printed or downloaded directly within Facebook itself, without taking users off the site — a first for Facebook, according to Valassis’ chief digital officer Jim Parkinson.RedPlum Social Savings, as the app is called, is part of Valassis existing RedPlum service, which includes iOS and mobile web apps for redplum.com and save.com and, soon, an iPad app and already covers some 100 million users. What the new Facebook app is doing is making that couponing offer significantly more social: with the app integrated with Open Graph, users will be able to share their coupons with other users, and advertisers can create their own coupons via a white-label service which they can subsequently target to specific users — so, like a Sponsored Story, the coupons can run in a user’s Timeline and act as another form of marketing for a brand. The coupons will appear on Facebook’s mobile as well as desktop versions.And while users are not able to redeem the coupons, you can see how this could be the logical next step — not just adding the coupon directly to a user’s loyalty card as you can already do, but pre-paying for them in the process. This is something that Parkinson says is being seriously considered by his company already.