The last place I worked wasn't a particularly great place and there were more than a few nights where we were working late into the evening trying to meet our sprints. The team while stressed out got pretty close and people started bringing in little mind teasers and puzzles, just something we would all play around with and try to solve while a build/deploy was running for the test environment, or while we were waiting for the integration test run to finish.
Eventually it turned into people bringing chess boards in and setting them at their desks. We would play by email sending each other moves in chess notation, but at a very casual pace, with games lasting sometimes two or three days.
Management tolerated this when we were putting in overtime, but as things were being managed better and people weren't working much more than 40/wk, they started cracking down on this and told us that we weren't allowed to have chess boards at our desks, although they were okay with the puzzle games.
What are the pros and cons in your opinion of allowing chess during software development lull time?