No saltier than ordinary bacon.
I think the issue is more that it'd be way too fatty to produce a proper burger. Also: crunchy.
Most of the fat renders out during cooking and bacon is only crunchy if you cook it until it's crisp. Bacon really is too salty to make into whole patties unless it's uncured, in which case it's not really bacon, it's smoked ham! You could certainly do a burger made entirely out of pork belly, but the problem there is that it wouldn't taste much like a burger or much like bacon. And there's the problem - when you take all the beef out of the equation, is it really a burger anymore?
Personally I don't really think bacon has a place on or around a hamburger. I know Bacon is a pretty standard staple burger topping, but I find that it's impossible to tell it's there if you have lettuce and tomato on the burger, in which case it's just another 50 cents tacked onto the cost of the sandwich. If you're going to cut the beef patty with anything, cut it with sausage. 50/50 ground round and pork sausage is fucking amazing and most of the burger shops in Oklahoma make their burgers this way. Other burgers just don't compare. Seriously, you haven't had a hamburger until you've had one made in Oklahoma. We might have a lot of really stupid rednecks and a really intolerant and awful state government but we know how to make a god damn hamburger out here.
