One flaw: You're not locating anywhere near all of the people that registered using this method because I bet a lot of people have never commented. In one website's database that I've got access to, almost 70% of the users register without ever doing the expected main activity. Unless you spider your copy of all the comments to cache home pages, follow the links off of friends lists and include other links to home pages around the internet (like Google does, which is why I chose Google instead of wget), you're probably missing a huge proportion of the profiles. You may argue that counting active users is more relevant than counting total members, but these guys might be voting on our posts and comments, and if they outnumber us, they've got more influence over the content than we do.