What's the history behind cam rips of movies and where have they typically came from?

I've seen a few throughout my life at friend's houses as a kid during the age of Limewire. Typically they were pretty good quality even though you'd see the odd person get up from their seat or hardcoded subtitles. Lately I've been curious about the history behind them and how they came to be.

Have there been well known release groups similar to the game cracking scene?

Have they always been mostly from one region?

Are they released strategically for one reason or another?

Have there been hidden methods to bust groups after a release such as steganography?

I'd be down to hear any facts about it you find interesting, stories, and if you have any articles or videos about the subject.