I made my first comment on StackOverflow. It's a site for questions and answers for the developer community at large.
The only thing that compelled me to try (and succeed!) leaving a comment was their OpenID support: I am so done with creating a new user/pass for sites that I only bother with it if I feel I'll be using it a lot. Not so good for drive-by comments and contributions.
However, some OpenID enabled sites demand you register and create a user/pass for that site in addition. I understand why -- account recovery if your OpenID provider vanishes -- but in my mind that negates the the value add-in for OpenID. I wouldn't be using OpenID if I thought my provider was just going to ninja-vanish on me. If stackoverflow.com had done that to me, I probably would have left without bothering. It's just one comment after all, and I only visit the site once every few weeks, max.
Still, nice to know someone gets it.