Forum Moderators: open
I have been researching this for a few months now here is my findings.
The more I posted a day to WebmasterWorld, the more hits I got! Sure I get traffic from other parts of the world, but the kicker is people clicking on your profile trying then going to your web site.
I have made many contacts within webmasterworld and made many trades between sites boosting my linkage and their linkage. The more I post a day the more people click on my profile then goto my webpage.
Its amazing yet stunning facts from months of research.
I now feel more free to actually participate in WebmasterWorld just for the sake of the larger community, and not worrying about traffic or SE's not liking my opinions.
One good reason to list (mentioned above) - credibility. There are quite few people here (not naming names ;)) who speak at length about building PR, or the dangers of slick designs, or whatever their pet topic may be. But when you go to check their profile to find a site they've done (to see how they implement their own advice), there is nothing there.
The site in my profile may not be perfect, and it is puny compared to some of the 10,000 page monsters some here put together. But it makes money for me, it is representative of what I do, and it right there for everyone to see.
To me, profile sites are like a resume. Just my opinion.