As for fingerprinting, that's a whole 'nother can of worms. I've never seen it be used for DRM specifically but it has been successfully used many times to track down who was leaking trade secrets etc. In fact it might be more widely deployed than most people realize.
The problem with fingerprinting for DRM would be the plausible deniability of an unsuspecting user "getting hacked" and then their fingerprinted copy ending up as the illegally distributed one without their knowledge or control.
>Other tech is meant to leave a trail leading back to forgers, a bit like a DVD ripping software embedding your MAC/IP information in any Mp3 it generates.
It is simple: rip the media multiple times with different identifying information, and then analyze the diffs (or just take the average). You cannot hide the existence of steganographic data if there are multiple copies with different steganographic data. It is not like analog where a loss of precision is justifiable
There are actually a handful of technologies meant to survive the transcription process only to reappear in the new medium. Probably the most effective schemes are used in money, in paper bills. There are little things there (ie the eurion constellation) that are purposely designed to be scanned. They can be copied. But then they are detected by software (Adobe Photoshop) and hardware (high-end printers) which then refuse to edit or reprint them.
https://en.wikipedia.org/wiki/EURion_constellation
Other tech is meant to leave a trail leading back to forgers, a bit like a DVD ripping software embedding your MAC/IP information in any Mp3 it generates.
https://en.wikipedia.org/wiki/Machine_Identification_Code