I'm going to be doing a full day xp workshop in about 2 months. This will be the first xp workshop I've done, and pair programming is one of the things I'm still concerned about being able to explain effectively. There is still a very common mentality of code ownership (developer owned and not team owned) that is hard for many developers to overcome. I think getting people to understand the need for pair programming and collective ownership of code is probably getting simpler these days because I think of lot of developers are beginning to understand the positive impacts.