What's the name of our site?
AskUbuntu seems to be more popular currently, but that could just be that it gained some initial momentum somewhere. Our FAQ, however, says:
AskUbuntu is a Q&A site...
The name answer says Ask Ubuntu, which is also how the site is identified when logging in via a Launchpad OpenID (and maybe others? haven't checked). Stack Exchange convention is to use a space for the site name, and the site names generally looks better that way.
Personally, I'd rather see Ask Ubuntu, but it's not a big deal and I've been going with what has seemed the more popular choice.