White Label Social Networks can be compared and TechCrunch came up with 9 Ways to Build Your Own Social Network comparing Ning, KickApps, CrowdVine, GoingOn, CollectiveX, Me.com, PeopleAggregator, Haystack, and ONEsite into one view, where features are compared of each network.

Here's the one page Survey of 9 Ways to Build Your Own Social Network; TechCrunch writes one or two paragraphs on each social network in the same post (I'd suggest reading the whole post).

I built a White Label Social Network, invite only, for the Social Media and Community Committee of the Web Analytics Association using Ning in about 30 minutes – it was great!  But while Ning worked for what I needed, it would not work for everyone, and KickApps, for example, focuses on medium to large websites that need to enable (add) Social Media Applications to their existing site while Ning requires you to host your Social Network on their servers.