Facebook e-commerce could be getting a lot easier for everyone with a new offering from Payvment that provides a shopping cart service that can be networked between participating retailers.

The beta application introduced at PayPal X Innovate09 in San Francisco lets shoppers move between stores putting purchases into a single shopping cart, Christian Taylor, Payvment’s founder and CEO, explains in this building43 video.

After browsing through stores on Facebook, shoppers can check out in a single transaction for purchases from multiple stores, says Taylor. Individual payments to retailers automatically are distributed.

Payvment developed the system using PayPal’s new Adaptive Payments APIs.

The free integrated system is built on Payvment’s existing shopping cart Web service. Retailers can add it a Web page by adding a single line of code.  Retailers also can customize their shopping carts.

The free system supports payments in more than 20 of the world’s currencies, according to Payvment’s Web site.