Well... I'm not exactly an expert on anatomy or anything, but that being said:
I don't really see why the tail would be any more of a problem to us than it is to animals. Yeah, you can say it could get hurt, but if you step on a dog's tail hard enough, it's going to get injured too. But if a dog's tail is broken, the dog doesn't become paralyzed from the waist down. It just ends up with a broken tail, and that's it. When animals have their tails docked, it usually doesn't affect their health in a large way either.
Tailbones are designed differently from the spine's vertebrae. They are also separated from the actual spine by the sacrum (piece of bone that joins the spine to the pelvis). If a tail is pulled, it surely would be uncomfortable to say the least - but again, if you do that to an animal, they don't like it either. That's why you just don't. It would not be like yanking on your spine, however. Because the sacrum separates the spine from the tailbones, it would probably yank more on your pelvis rather than your back.
And, on top of all that, tailbones are often surrounded by some kind of protection, be it muscles or cartilage. So it's not like you'd just be sitting directly on bones. It would be cushioned in some way.
Plus, there are some animals that do occasionally stand on two legs, remember. Monkeys and lemurs walk/hop along on two legs when they feel like it, and kangaroos use their tail almost as a third leg. And that's just a couple examples.
I don't see why it's that unreasonable to think tails would be impossible on humans. We all develop with a tail anyway as an embryo. It just goes away before birth.
Topic: The Tail... (Read 2163 times)