Mike,
It's not something that's limited to turning; happens in every artform. Indeed artists used to be trained in technique by copying masters' work, and you may still see a painter set up inside of a European museum doing just that. I've known a few painters who could make you a dead nuts copy of a Rembrandt, De Vinci, Manet, or a half-dozen others. When I was teaching, a fair part of what my students did was study the work of others, not to copy, but rather to understand and begin the process of creative thinking. Invariably some of their work would resemble what they had seen and studied.
I appreciate every artist's desire to "protect" their ideas, and thus preserve the uniqueness of their contribution. I also acknowledge that even "known" professional artists can be a little insecure that someone will copy their piece(s) and 1) do it better than they, 2) use the pirated design to make money, or 3) both. This is not limited to the art world. Examples: Oneway screaming about JET "ripping off" their componant live center design and selling it for $20 less, and all the patent and copyright litigations in courts around the world.
My favorite story on the subject concerns Pablo Picasso. He used to drive art dealers crazy when they were trying to authenticate a painting as having been done by him. Part of the problem was that the man produced such a huge number of paintings and other items, and part was because his style was so easy to copy. As the story goes, when someone would bring in a piece for him to verify as his, he would chuckle (because neither he nor anyone else could remember all the stuff he did), and then seriously look at the piece for several minutes. Finally, if he liked it, he verified it as his work. If he didn't like it, he denounced it as a forgery and would point up its faults.
It didn't matter whether he had actually done the piece or not!
Mike, I sincerely hope that you get to the point where others are copying your work.
Mark