The Prisoner's Dilemma is a classic problem in game theory. Wired is covering the sucess of a new stratagem against Tit for Tat, which won the original Axelrod Iterated Prisoner's Dilemma competition.
In this year's recreation of Axelrod's classic competition, the winners, from the University of Southampton's Intelligence, Agents and Multimedia (IAM) Group, put forward a solution which allowed their entries to collude together, rather than compete with each other.
The Southampton press release doesn't cover the topic in much detail, but does they do say that "No outside communication is allowed so the agents have to recognise one another by playing a specific sequence of moves at the start of each game". A lot of people have complained that the Southampton entries into the contest were somehow cheating. This somewhat misses the point of what the Southampton team was trying to accomplish.