In the Internet piracy scene,
Watermarks on releases can come from a variety of sources.
Many releases come from Asian silvers and those silvers are tagged by those responsible usually with a letter or logo watermark in one of the corners.
Many DVD Screeners, especially Oscar screeners, will have a movie studio watermark in one of the corners in an effort to curb piracy of those screeners.
Watermarks by Disney are numbered so if a copy is leaked it can be traced back to the academy member.