It's an interesting topic. I'm just getting into the swing of 3D printing. I'm hooked now. But, I don't have the ability to create my own models just yet. So I've found thingiverse and sites like it, and I'm really enjoying them. I'm finally seeing where all the 3D printed stuff on ebay that I've wondered about for years are coming from. And it crossed my mind that it's just part of the hobby that people are going to print and sell stuff they did not create. Especially Andrew's Deckard blaster.
I like Thingiverse & My MIni Factory allowing for open dialogue with the creators of the models you download, and for compensation. I don't usually download a model I'm not going to print, and I don't download a model without leaving a tip. Unless the creator doesn't allow for tips of course, but when that happens I usually ask the site to let them know I tried to tip them.
When I'm finally able to create my own models, and I start sharing them on sites like thingiverse, I will do so knowing that some people are going to print the models and sell them. My intention is to ask for them to contact me first, and then just give me a few bucks every time they sell one. But that doesn't mean anybody will. I'm not going to try and sell anybody elses work, but I will sell my own.