Just went in a store trying to trade in some games and an agent told me I hit the trade limit... but I haven't traded like 2 months, and last time I traded I only did about $200, with no duplicates or new games of course. Any changed rule for a trade ban?
A couple people have mentioned getting trade banned and not knowing why.
So unless you track trades in excel, or whatever, then it's hard to say what could have been the reason. If it's not 4 copies of the same game, going over the $500 cash limit, or going over the $2k trade credit limit, it may have just been somebody looking into your account and not liking what they saw (if you're a regular trader).