Originally Posted by jcat
...I feel "intuitively" (I'm not sure that's the word I want) that there should be a "line", but don't know where it should be drawn. ....A fox, coyote, spider monkey, possum, or lynx is presumably less dangerous than a chimp, lion, bear, water buffalo, or hippo. ...I don't feel that size alone should determine whether a dog is a potential danger...I doubt that this question can really be fairly answered.
[Above quote was condensed]
That's why bans are more appealing...they are 'simpler'. It doesn't take a panel of experts to make a ban. It does take a panel of experts to make regulation.
Not a single person in the world knows how to properly care for every single species of animal in existance. Zoos aren't run by one person, unless the number and variety of animals is quite small. Most larger zoos have at least one veterinarian on staff if not many, and they rely on many trained individuals to be experts on the animals they are charged with caring for.
With private ownership, it is rare to see more than a very small number of animals, and even rarer to see a wide variety of species. So there is an advantage in private ownership. An owner of a Tiger only has be concerned with knowing how to properly provide for the needs of a Tiger.
I personally wouldn't be comfortable with owning an animal much larger than a Jaguar. However, I know plenty of people that own tigers or bears or large snakes. These animals are all out of what I am personally comfortable with. But these animals are thriving under the care of their owners. They are happy, they are healthy, and they interact great with their owners. Just because owning these animals is out of my comfort zone, does not mean that it is impossible, or irresponsible for someone who is comfortable with and able to provide for them, to own them.
If a line has to be drawn, it should be based first on personal comfort with the type of animal, then on the ability of the owner to provide for the animal. The first is a personal choice, the second will ultimately be a testament to the first. Legally though, the second is the only way to ensure responsible ownership. So any regulations put into place have to have at least some form of measuring the comfort level of a potential owner. The simplest means, is to require experience with that specific species of animal prior to allowing for ownership.
As with anything, there will always be a small degree of failures. Regulations can ensure a high level of successes, whereas bans can only guarantee that the will never be a chance of success.