OpenID is a great idea. One that just might not work. “This post”:http://miksovsky.blogs.com/flowstate/2007/08/openid-great-id.html does a pretty good job of summarizing some of the problems.
For another example, try logging in to any 37Signals app. I’m reasonably clever but the first few times it took me _forever_ to finally authenticate. Or maybe I’m just not that clever.