I've used (and broken) a few kinds, including the crappy elastomer+spring clamp-on hitch on Bell 2-kid-type trailers.
I've made some from different things, including copying an air-hose-coupling hitch others have used successfully, and most of them broke under the loads and road conditions I put them thru. :/
The only homemade one I've used that survived was made from bike headtube/steerer parts, as seen early on in the DayGlo Avenger thread. Even that had two failures, but IIRC both were nuts unscrewing from bolts mostly because I didn't use loctite or proper locknuts or lockwashers. The hitch itself was very durable, though.
Now I am using automotive ball-hitches, and so far have had only one problem, where somehow the nylock nut on the tongue clamp worked it's way up and allowed me to unhitch it, but then wouldn't let me hitch it back. It's also possible that someone messed with it to do that, but I can't see how they could've gotten to the nut. It has not had this problem again, which favors the latter theory.
I"m sure they're overkill even for my stuff, but I'm all for overkill if it keeps me from having any kind of problem that results in a trailer coming loose while a dog is in it, which happened once with Hachi.
One thing that my hitches have to deal with, is very large dogs wiggling around while I ride; this wouldn't be happening with normal loads that most people carry.
Elastomer hitches might work ok for that too, but my experience with the Bell trailer versions shows it would need to be a lot better than those.