Palo Alto, Calif. - Ning, a free service that lets users create their own online social networks, has raised a $60 million fourth round of venture capital financing from unnamed investors, PaidContent.org reported.

The company had a pre-money valuation of $500 million. Palo Alto, Calif.-based Ning was founded in 2005 by Marc Andreessen -- who also created Netscape and Opsware -- and Gina Bianchini.

"We raised the money to enable us to keep scaling given our accelerating growth (over 230,000 networks on Ning now, growing at over 1,000 per day) and to make sure we have plenty of firepower to survive the oncoming nuclear winter," co-founder Marc Andreessen wrote on his blog.

"At current growth rates, we don't need it to get to cash flow positive, but having lived through the last crunch, it's good to be conservative with these things."

Related Links:
http://www.paidcontent.org/entry/419-fc-omg-like-totally-ning

http://blog.pmarca.com/2008/04/ning-news-serie.html