The Microsoft and NBC Universal News joint venture MSNBC has acquired the Newsvine community of citizen journalists for an undisclosed sum.

Newsvine, based in Seattle, publishes stories from both the mainstream media and a community of users together on the site. Users can vote on their news stories of interest, similar to the Digg or Reddit “social news” sites. Newsvine’s services also include group discussions and a conversation tracker.

The site gets over one million unique visitors each month, and is currently ranked at 4,173 by Alexa (see the graph comparison with Digg and Reddit below).

For more views on the acquisition, check out Read/Write Web, CenterNetworks, and the Center for Citizen Media.