Question: Are you finding that as more people join social networks that the value goes down due to noise and difficulty adding quality contacts?
My Answer:
I find that it's the exact opposite, the more people who join social networks increases the odds that I'll find more quality contacts. The pool of "early adopters" for any new networking site is going to be small and narrow. When a site breaks out from being just early adopters, they pick up a wider range of people with more diverse careers and interests.
There are a lot of folks whom I consider professional colleagues that wouldn't consider joining a social networking site unless it offered them more than just professional connections. Colleagues who have secure, full-time jobs often don't come to an on-line forum with the notion of expanding their business. Unless there's a wider range of people on that site, say others from their city, folks who share outside interests, school alumni, etc., they'll just take a pass.
I'm all for as many of those folks being here as possible! There may come a time when I'll want to tap their expertise on a subject, or hire them for a consulting project.
To address the notion of pay-based social networking sites, That's certainly the best way to narrow the universe of members quickly. I don't see where that would benefit me all that much, however.

