What particular factors might have begun to inhibit participation in 2006, when we know it began to stagnate?

That's a lot of useful information. I almost always come to wikipedia logged into my user account, and now that you mention it I *have* noticed that there are barriers to creating (and editing) pages anonymously. Like Bodnotbod noted, we need to try to see through the eys of newbies as we consider these questions; editing anonymously from time to time might help with that. Netmouse 19:24, 5 November 2009 (UTC)