OpenID has never really caught on in a major way. I use it pretty much only on StackOverflow and 37signals products, and I really like it. Regular (non-web-building) users find it puzzling, and don’t have a good understanding of URLs, let alone ownership of them. So it works for geeks, but not for the general populous, and therefore isn’t a good viable solution for most sites.
via OpenID Has Failed. So What's Next? -- All in the head. The quote is from a conversation with David Sklar.