Note that Ben (a personal friend) has been an enthusiastic user of Mercurial for several (4? 5?) years, and is pretty happy with it. He was even using hgsubversion for a while I think.
Note that there's a lot of social problems around DVCS, and the thing Ben worried about is still a _real problem_. I get potential contributors showing up with months of work, and it's an enormous pain in the ass (both for them to rewrite and for me to beg them to work with me) when they did something architecturally unacceptable early in the process that a simple 2 minute review could have caught.
But would the insecure people have done that work at all if they knew they would be forced to commit it publicly? Maybe so, but would it all be one huge commit to svn instead of maybe a string of more concise commits to git or mercurial?
I just envision someone insecure (like I feel at times) saying, well, I'll just clone this and play around on my own machine. Then after making some commits and building up courage, saying, OK, I'll try and go public with this. With centralized VCS that seems less likely to me. The insecure programmer just won't even try. I don't know, it's probably different for different people.
Note that there's a lot of social problems around DVCS, and the thing Ben worried about is still a _real problem_. I get potential contributors showing up with months of work, and it's an enormous pain in the ass (both for them to rewrite and for me to beg them to work with me) when they did something architecturally unacceptable early in the process that a simple 2 minute review could have caught.