Thanks to Techcrunch for the following analysis of the various offerings out there. The main differentiators are:

• cost – initial, on-going, development (their team vs. your team), hosting (their servers vs. yours);
• hosting – their servers or yours (if you care or worry about where your sensitive data sleeps at night, you may need to consider your own hosting.);
• features – group discussions, rich media, integration with other social networks, membership management, on-going applet/widget development, scalability – e.g. maximum number of members supported, customization options;

Here they are:

• Techcrunch – 9 Ways to build your own social network
• Techcrunch – 34 More ways to build your own social network and the comparison charts.

Lots of information to plow through but a good starting place to evaluate what options you have available.

Dean Owen