I'd like to throw up the idea of adding OpenID authentication to Kentico, especially now that you've added LiveID support in 4.0.

I'd say it's low on the priority list, but I'm a big fan of the tool and use it on as many web sites I create as possible. (The types of sites and target audience of course restrict it's use in some cases.)

Of course, you'd have to make sure it was robust enough. See http://www.codinghorror.com/blog/archives/001121.html for one man's opinion.