That was super interesting, but the article also provides evidence for a pet peeve of mine.
..first-time shoppers. They did mind registering. They resented having to register when they encountered the page. As one shopper told us, “I’m not here to enter into a relationship. I just want to buy something.”
Users don’t want to register to buy, and I also feel that they don’t want to register to comment on your blog, join your social network blah blah. That’s why I don’t like to make commenters register on my blog and also why I’m a big supporter of projects like Open ID and Facebook Connect, which allows me to share my profiles across many other sites.