I worked at a small museum in West Texas. All employees and volunteers had to be trained to not accept donated artwork. People would walk in and try to donate either their own work or the treasure they found in their attic, at a garage sale. We would have to tell them, you have to fill out this paperwork and present it to the board. It has been nearly 20 years so I don't remember all the ins and outs but there were major legal reasons for this.
The other were some employees. It was when the first digital cameras were available to the general public. I had one of the sony ones that you put the floppy disk it. They asked me to bring it over because they needed to take a picture of art pieces recently acquired (we had just had a major juried competition and pieces were acquired so that was legit). I figured it was either for the data base or as a place holder for some publicity until the official photographer could take pictures and develop them.
I get over there (I was at the children's museum down the street) and no that wasn't it. While the director, curator, and official photographer were out, the other staff decided to make postcards of the new pieces and sell them in the gift shop as a surprise. I told them you can't do that we don't own the copyright*. They kept arguing. Knowing them I gave them the camera - went into an office and called the former curator. She had left because of a family tragedy several years before, but still helped out sometimes. I told her what was going on. We agreed I would leave - had to because I had a field trip coming. She would drop by, discover what was happening, and explain copyright. If that didn't work she would contact Director, at his conference, so he could put a stop to it. Fortunately they listened to former curator. We also had staff development on copyright law.
*For some reason the Director had thought it was a good idea for a dyslexic to proof read some of the paper work. I pointed out this was a bad idea, but had gotten to the part were the artist specifically still owned the copyright and we had permission to use photographs for insurance, promotion of exhibits/the museum, and a catalog for loaning out items. We could not sell reproductions of the image. I asked him about it and he said - The artist maintains ownership of the copyright of a piece of art unless specifically released to the buyer. The buyer owns the object the artist still owns the idea.