Recently I had need to attach multiple backbone.js Router objects to the same route; the purpose was to create a page which could have multiple sections that were unaware of each other, since the path gave them all the information they needed. This allowed a much looser form of coupling and gave us a bit more of a MVP feel rather than a traditional MVC.
However, after a lot of discussion we ended up scrapping this plan for a slightly different one. I had already written a patch to make backbone.js routers support multiple route handlers, though, and I didn’t think it made sense to just throw it out, so I’ll provide it here. Keep in mind that this may not work with future versions of backbone.js!