Business week reports plans by many social networking sites to bring in third party developers to attract more users.  Some sites opening up their networks include Facebook, Myspace, Linked-In, Friendster and Google’s Orkut. Virgin Mobile became one of the companies interested in these mega-networks.Vice President of Value Added Services Dom Tolli wants Virgin’s four-point-six million customers to browse their preferred social-networking site. Virgin has access to an application program interface to satisfy the needs of many members. The API programs help developers create new functions to communicate with existing programs. E-Bay’s senior manager Adam Trachtenberg understands why businesses need to obtain third-party developers.“Social networks have reached a point of maturity, and opening API’s will help them grow.”eBay made software available for others to connect to its site, and web site owners post around 40 percent of its listings. Marketing Director Jeff Roberto opened Friendster up to its software around six months ago showing the visitors increased to 17-point-six percent or up to 18.8 million people.“This is our biggest month-over-month growth since launch.”Facebook, orkut, and Friendster verify making their software available to developers. Myspace declined to comment.