I have a similar experience with sporting activities with people in the office. Every week at work we get together and play floorball ("innebandy" in Swedish). It's a mix of people from all departments, and invariably I end up talking to all of them (especially on the way back to the office). Apart from having fun playing sports, I now know various people in different departments. This is good in many ways, not least when you need something done and need to find somebody to talk to. Of course this only works with people that join the particular activity. Nevertheless, I've found this "random connections" very useful.