I'd think ~most~ little dogs that are used to going places would be fine... It's just some people who might be tempted to bring spoiled precious with them... or people with cats that I think might be a disaster often enough. Even my cat that travels pretty well will yowl if he's in the cage long enough or he's bumped around and tired of it.
You're right, of course, cats tend to be a little more reluctant to be carted around than dogs. Plus they can make noises that no earthly creature can imitate.