The music industry is a good example of that. With a single song you have a copyright for the owner of the musical score and a copyright for the owner of the lyrics (not necessarily the creators of the music and lyrics or the same owner for both). If anyone performs the song, you would need to pay a license fee to the owners for 75 years beyond the death of the author in some cases (often the owner had nothing to do with creating the music and none of the licensing fees go to the real artists or their families).
Next, you have a phonogram copyright on recordings of a performance (donated by a circle with a letter P inside it). This is the one that can go on forever. Record companies can release new copies of old music just before the old recording's copyright expires. The license fees to the owner of the song were already paid for the original performance, and since they are just re-releasing the same performance they don't have to pay another license fee. But they can claim a new extension to the phonogram copyright.
So, say you digitize a record whose copyright has expired and give it away for free on the internet. Record companies can muddy the waters enough to claim you just copied one of their re-releases instead of a public domain record. You are guilty until you can prove yourself innocent.
On the other hand, record collectors would say that without this behavior, old public domain recordings would be lost forever.