There were several campgrounds in Yellowstone that did not allow tents, tent topped popups or trailers with tented slide out beds when I was there 5 years ago. The sad truth is that there is no such thing as a bear proof camper (especially those mass produced mega RVs). If a bear wants in, it will get in. I have seen pictures of RVs with the entire rear end ripped off by a bear. The only reason to ban the tents is that bears are smart and always go for the easiest pickings. When the easy way is gone, they will start working on the more difficult stuff. In many places, they have figured out the whole bear bag thing. Even hanging your food in a tree won't keep them from the food. A teardrop should be allowable as a hard sided camper, but I wouldn't keep smellables (food, perfume, deoderant etc.) in the camper in bear country. I wouldn't even cook up wind of the camper, but in those grounds, every one is so close together that the next guy's food smells could attatch to your camper and still have you getting looked at. The small campers will be the first ones that the bears will start investigating as they are less intimidating, but none are safe.
Bill