Worst thing that can happen to you as a producer is to realize that one or more of your beats have been transformed in a new product and used in commercial or non-commercial applications, without your knowledge or approval.
Your beat was practically stolen!
2 Ways your instrumentals can be stolen:
a) With a software that can download the beat directly from instrumental selling websites, beat stores or youtube. (many times after listening to a beat the mp3 file will remain in the browsers cache folder and can be simply copied without the need of additional software.