That "I have too many games and I need to get rid of them to make room for more".
It usually ends in remorse. I end up selling something I wish I had held on to.
While I am not parting with my 4e collection (just yet) I am thinking of getting rid of one or two of the basic sets that were out for 2e, Quest of the Ancients (I have 2 copies) and maybe SuperBabes.
A few other items from the recent Free RPG day. No idea just yet.
I have a game auction I normally sell these things at, but that is not till October.