Hi,
I never felt comfortable with any of the scripts that I looked at. The design and programming were problematic, and they had very little spam protection. My site would be fried within a week with the weak spam protection that the scripts provide.
I haven't tried any of the hosted social networking sites, but you may want to take a look at
SocialGo. Ning is another big one, but they recently raised venture capital, and with the VCs in there I don't trust them. There was a big brouhaha recently because of the heavy handed way they took over user data and refused to release it. You will have to google to get the details.
Hope this helps,
Rich