On a related note, this happened in a Dominion map.
Player A contacts me, suggesting that he'll give me his remaining control points (we both had two) if I then join another Dominion map with him and give him the control points in the second map. I refuse. Two weeks later, Player B allows him to walk into the final control point (right of way, war, right of way), and they both fight me to prevent me taking any of his four points before the timer is up. I assume they collaborated on another Dominion map afterwards.