The model contains a regex and a priority that i think is supposed used to figure out which backend to use automaticly. The priority is used to break ties so we can have fall backs for things like embedly with regexes that look like .* 

A model is nice so we can override it, but a choice field would be fine with me. I think it would be helpful for me to show you what this looks like inside of our cms. You have a account ont he bay citizen, I can make it staff and send you a link if you remember your password/facebook login.