The housing projects over here banned Boston Terriers as a dangerous breed of dog. I know a handful of people who have gotten upwards of 50 or even 100 stitches from smaller breeds like westies, dachshunds, pekinese, and heard of someone losing her leg after a lab attack (not sure if that's true). I also know multiple infants in this area alone have been killed by JRTs, one was killed by a pekinese, etc.
So yes, I do believe all of these bans, whether in townships, cities, or simply by building, are due to the dogs being "vicious" or "dangerous". And I also know that EVERY dog, regardless of breed, is potentially dangerous.
ETA: @ pitbullfriends: while I don't know any specific pug bite cases, a pug could definitely cause someone enough damage to require many stitches, break small bones, and could do much more damage to a small child. No, they aren't going to be able to do the damage to an adult person a pit bull terrier or any other large breed dog could, but they can do a LOT of damage.