Regardless of the past confusion with wordpress.com and wordpress.org (which I think is overblown), Auttomattic/Matt choose to keep it that way. Therefore, it makes perfect sense to me that talkpress.org (bbpress) would be the self installed software while talkpress.com would be the hosted solution JUST LIKE WORDPRESS. At least there would be continuity. BB, which stands for "bulletin board" is a lot less hip than "Talk".

As a domainer myself, I can tell you its true, a fair percentage (surprisingly) of people do type in the domain in their address bar and the .com TLD is almost always the extension they use under that circumstance. Just because you or people you know don't do it doesn't mean others won't. In fact their have been many millionaires made within the domain industry based on the very fact it frequently does happen.