content: One of the best and most clear examples is Disney, I think.  Here is a list of 50 films Disney made from stories/characters in the public domain.  Many of those films would be IP violations if they were made today, thanks to laws lobbied for by Disney themselves. Create a business model, make billions of dollars with it, then use those billions to lobby to make it illegal for anyone else to use the same business model once you control the market.