This thread is funny. Cross breeding is happening in the WILD...TOO!
I personally have a wild SP. Look at aquascapes "going to the jungle" thread, he has a good example of a cross bred motoro that is "wild" So it is going to happen if you like it or not just my $.02..
Nothing is wrong with it unless they are labeled something else as TB said. They need to be labeled as such.
Yes hystrix x motoro is a cool breed. Look at some of big daves threads he has pictures of the cross he had, very neat raY!!!
I think it can be a great idea for hobbiest as we can produce an "aquarium ready" ray that can be kept in smaller enclosures by breeding smaller rays together.