I posted the following on the official Steam Suggestions/Ideas board:
I'm sure that every Steam user has games that he/she doesn't want anymore for various reasons. Giving users the ability to gift owned games would probably result in the creation of a digital second-hand market which I wager is something that the publishers and Steam would want to avoid at all costs.
So the only thing that's left as an option is to allow users to trade-in games to Steam directly.
How would it work?
Users would receive about 20% refund of either the current or the paid price, whichever is lower (there's no sense in refunding 20% of a 50€ game if it was bought during a Steam sale or if it was bought years ago when its value was higher).
The refund would go directly into the user's Steam Wallet which would ensure that Steam ultimately gets that money back.
Users would be able to get rid of unwanted games and get something back, but more importantly, it would cause people to open up even further to digital distribution. I also think that people would be more receptive to fully-priced games instead of waiting for deals. This may not be so significant for high profile games such as Call of Duty, but lower profile/indie games would definitely profit from this.
I believe this would benefit both gamers and Steam greatly. Steam's sales/profits should increase as users would be more open to impulse buys and buying a game they're not quite sure about. Most likely people wouldn't be waiting for deals so much knowing that if they hate the game or something, they could still get something back for it. Then they would forward the money for another game - and so on.
Ideally, something like this is already in the works and this is the real intended purpose of Steam Wallet. If not, hopefully you will consider it.
What do you think?