Receptive audience
While no one likes to be approached inappropriately, you'll find people in networking sites more receptive to an informational phone call or email exchange. On LinkedIn, for example, you can specify whether or not you're willing to accept contacts regarding deal proposals, and you can limit your searches only to people that are. In the discussion boards, blatant advertising may not be allowed, but you won't be accused of making a sales pitch just for sharing your expertise.
Easy group-forming
Growing a discussion list or forum on your own site is no easy task. In the social networking sites, there's a built-in audience looking for groups to join. Groups have a visibility within the larger environment that simply doesn't exist with an independent community, or even on a broad open site like Yahoo Groups. People really will start signing up almost immediately after you create your group, if you offer value to them.
Get visibility into the networks of your connections
The ability to see your connections' connections, and to determine who you know that can make an introduction to the person you're targeting, is very powerful and has no direct parallel in face-to-face interaction. In fact, it's so powerful that entire products are created just around this ability. As Contact Network founder/CEO Geoffrey Hyatt says about his company's product, "It's a one-trick pony, but it's a very valuable trick." Jeannine Solanto, CEO of Foundation Systems, reports that her company has cut their sales cycle by 15-20%, on average, by using Leverage Software to gain access and influence within target accounts.
You can realize these benefits immediately with the existing technology, regardless of its imperfections. In many cases, you can just use the free service, but even the premium memberships only run a few dollars a month -- chump change if you're actually generating business. So the real ROI question isn't whether they're worth the money, but whether they're worth your time. The answer is "yes" -- not because the sites themselves are, but because the relationships are.
Online networking sites simply help you manage more relationships with less effort.
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