Motivation: I once had one surplus card on my hand, and knew the robbers would come soon. So I gave it to someone for free, to avoid losing more cards when they hit.
I was surprised by how badly this was received. Two of the three other players (the hosts of the game) acted upset, like I had tried to cheat. I had to take the card back, get robbed the next turn and 'giving cards away for free' was banned immediately. (Oh, how I hate mid-game additions to the rules. But that's beside the point.)
So now the question: Is this really illegal in Settlers of Catan? Is it generally considered underhanded in any way? If so, why?
My reasoning was like this:
Awants to give
rockto B, in exchange for
Atrades the received
wheatfor the (formerly his)
Bnow both have the same resources they had in the beginning, only the sheep has moved from