well a lot of people have jades as bonsai, they can even be seen in a lot of bonsai books. For anything to be considered a bonsai it must look like a tree which has become miniaturized. If you have a young tree which is small because of it's age, then it is not considered a bonsai, however, once it has been trained in some way to stay small, it can be considered "bonsai," or plants in developmental stages can be considered "pre-bonsai material." So to answer the question, jades can most definitely become bonsai. I know people who have ponytail palms and they consider them to be bonsai, and there are many types of bamboo that are considered bonsai, however "lucky bamboo" I don't really consider to be bonsai. It's all about what you think though, if you told people that what you had was bonsai I don't see any reason for them to disagree with you.