Routes and namespaces
As I've said in one of my previous posts, you can have 2 controllers with the same name, but on different namespaces. The problem with this approach is that you'll only be able to get a route by specifying its name. So, if you don't want to use a name or if you can't (for instance, if you're using the HtmlHelper.ActionLink, which simply doesn't let you specify a name), you're out of luck.
Steve Sanderson extended the Route class so that you can indicate a namespace when trying to get a route by controller name from the route collection. It's still a bit rough, but it should point you on the right direction.