The main reason for not crossing garter snake subspecies is because the only real thing that separates garter snakes are their coloration and pattern... scale counts and all aside... lets face it, if we had a pure white garter of every subspecies we would not be able to tell what one was which subspecies. having said that... there is no way to make anything more exciting by corssing types of garter snakes. They are already as impressive and beauitful in their natural form as they will ever be. Mixing up two is going to give you a snake that, in the hands of the inexperienced, will be passed off as either one or the other and will end up muddying genes down the line. The problem is that a lot of people (as in not the ones on this forum) treat garter snakes as all the same. Often at shows you will see a garter snake labeled just that... "garter snake"... with no regards to its species or coloration. hybrids of garter snakes will look so similar to one species of the other that they will end up being mislabeled and their true identity lost. Then as they get passed around the trade... they will be introduced to pure animals and pure animals would become increasingly rare... kind of like carpet pythons. It's rather hard to find a truly PURE diamond python, or even a true carpet python... they have been intergraded so much that now most of the carpets out there have diamond python in them somewhere. Heck the carpet python I bought years ago was half diamond (Still have her, Kisses is a pet of mine). When you cross animals that look the same aside from their actual coloration... it is very hard to tell when the resulting animals are hybrids or intergrades. When you cross a ball python to a burmese python... well... you know what you are looking at! And I have got to admit, some of those crazy crosses, as unnatural as they may be, are extremely intriguing and beautiful creatures. So I would not say that they are altogether worthless. In fact, whether something is worthless or not, is totally one's opinion... as in:

I totally consider any cross between subspecies or species of garter snake "worthless". While I do not believe the animals need to be euthanized, I do not agree with intentionally producing them for the reasons stated above.

I do not consider all hybrids worthless... the ones that are such obvious crosses it is impossible to mix them up with a pure species I find to be quite awesome, unique, and deserving of their own little niche in our hobby. The carpondro (carpet x green tree) is easily my favorite.