Update - Xbox One
Microsoft elaborates more on their polices regarding borrowed and pre-owned games.
"Trade-in and resell your disc-based games:
Today, some gamers choose to sell their old disc-based games back for cash and credit. We designed Xbox One so game publishers can enable you to trade in your games at participating retailers. Microsoft does not charge a platform fee to retailers, publishers, or consumers for enabling transfer of these games.
Give your games to friends:
Xbox One is designed so game publishers can enable you to give your disc-based games to your friends. There are no fees charged as part of these transfers. There are two requirements: you can only give them to people who have been on your friends list for at least 30 days and each game can only be given once."
So apparently they wont have any specific fee to sell your games to retailers like gamestop etc. but, they have a set of requirements if you are to borrow a games from someone you know...? Still seems a bit shady but at least they are clarifying the situations a bit...
Stay tuned for more Xbox One updates