Facebook is testing a new Buy button with a select group of retailers that lets you instantly buy products — without ever having to leave Facebook. When you click Buy, the entire transaction, including entering credit card and shipping information, takes place within the social networking site. Facebook told TechCrunch that while its not taking a cut of sales for purchases made with the Buy button, it wont count out doing so in the future. Facebooks new Buy button is only being tested with small and medium-sized business in the US, the company says.