Colorado is a counter-example to the assertion several people have made that if sailboats are registered they must also be titled. The park service handles registration, and there are no titles. Certain small water craft, like kayaks, are not required to be registered. Since the park service manages many lakes in Colorado and maintains the associated facilities, it makes sense that they should get a few bucks to do it.

Also, it's not terribly difficult to figure out where to put the registration numbers and annual stickers. The scheme seems to be the same in most states.

Boat trailers are another matter. A friend and I have both experienced numerous ridiculous problems getting used boat trailers registered and titled in Colorado. A minimum of three trips to the DMV!