Successful large companies are starting to use "social media" internally to manage development projects. JIVE is a leader, providing software that lets the latest generation of workers at major companies use the collaboration methods that they are already familar with. JIVE revenues (not dependent on advertising) have gone from $30M to $46M to $77M in just the last 3 years. That's nice growth, and its only just starting to catch on. The growth potential is HUGE!
You can think of it as "social media" within a mid-sized or potentially huge company. "Membership" is restricted to employees and costomers, and usage feels similar to the social media that you're used to. Its a brilliant concept. For more info, see http://www.jivesoftware.com . The ticker is JIVE if you want to look them up on Yahoo! Finance.