[danielha]

Both let you create social networks, but they're quite different. Ning seems to be more about hosting social networks that you create with your service -- your social network is standalone and is your own personal niche MySpace.

Crowdvine has a single community feel to it, with users joining multiple groups based on arbitrary titles ('Cool People Who Know Kati' is one example). It's more group-creating than social network-creating, which would be ideal for smaller scope congregation. Further, however, Crowdvine doesn't let you do anything once you're in a group besides read blog entries from other members.