Hmm, I think one way to look at this is that the most important part is the View and the Categories are actually less important, they could be considered like a filter. It could even make sense to have a View and no Category (to see 'All'), but here I am just guessing what you app could be doing...
The reason I am saying that is that I assume you are going to have 4 Backbone Views (Map, Livestream, RSS, etc.) but no specific views for those categories. So when switching categories, you don't actually switch view, you just re-render it with a different param, correct?
Then for me, the router should be something like:
'map/:category': '_map'
'rss/:category': '_rss'
...
One route for each main view, and the category as a param to the callback. People can then bookmark an url such as #map/events or #rss/places_to_eat but internally, you are managing 4 clean views.
Later, it'll be easier to use splats to allow for views showing multiple categories at once (splats start with a * in the route definition).
Just my two cents!