@ dillettante,

According to that wakipedia that article you liked to says:

Quote Originally Posted by the article
The watermark may be intended for widespread use and thus, is made easy to retrieve or, it may be a form of steganography, where a party communicates a secret message embedded in the digital signal. In either case, as in visible watermarking, the objective is to attach ownership or other descriptive information to the signal in a way that is difficult to remove. It also is possible to use hidden embedded information as a means of covert communication between individuals.
I put the important part in bold. Which, suggests HanneSThEGreaT was correct. Although, wakipedia is known for having some incorrect info.