I have to come out of the woodwork on this one - I'm a Big Brother fan and I'm not ashamed. I actually like the .net of this name, as I tend to surf a lot for news of the current show when it's on. Some people might prefer the plural version, but what I notice is that (over this side of the ocean at least) there is rarely more than one particular reality show on at a time - presumably because they would take viewers from each other.
Although Big Brother UK has a subsite set aside for it on Channel4.com when it's on, it occurs to me that diehard fans of reality shows would probably love to have a dedicated reality show site to keep them up to date with the current one and perhaps this could have a forum attached for discussions of the latest happenings, chat about old favourites and updates on what has happened to the various participants. So I think a website with this domain name would definitely draw a lot of interest.