Holmzini:
1. If you shop a track, you always risk the possibility of being plaigiarised. That is because you as a person with, I assume, an inconsequential legal expenditure can not fight against a larger entity that has more financial leverage than you. These people, producers or labels, can strongarm you in that sense.
2. If you shop a track, and even put a "watermark," it doesn't mean that the person can not simply remake the instrumental on their machines, and then lie and say that they never heard your music (unless you have some form of evidence showing otherwise.) You don't have the money to take the case to court, because it is too expensive. Or, they can change up your track and then make it "different" altogether.
3. If you don't shop tracks, nobody will ever know your work, and you will not get paid. So shopping tracks, and assessing the costs and the benefits of doing so is something you have to reason with. You want some income, so you have to shop tracks, right? But you don't want to be plagiarised? It's a calculated risk.
If somebody figured out a way for a person to safely shop tracks without having plagiarism occur, then most of us would already know the answer. Knowing that people on all tiers in the music business (from international to the local level) are rather devious in matters like these (either of necessity propagated by competition, or individual character) there is always that risk. It's comes with the territory.
*On the other hand, producers that have a little more clout, send their beat CDs to their connections within a label. A&R or another rep that likes your tracks will most likely make copies of the productions for others in their company, their artists. Then those connections, if they like your CD, will make copies for their friends and leak the production showcase CD out of the company itself to a larger web. This works as a good method of advertisement for the producer within a sphere of influence that is consequential to his/her career. With that said, it is still possible for people to plagiarise at that level, however, chances of it occurring seem less when you know the producer shopping the CD, or his friend in a personal fashion.
Sincerely,
God