We did code ownership, then very important developer left, and we did pair programming for a few weeks and then no code ownership (and people were assigned task

We did code ownership, then very important developer left, and we did pair programming for a few weeks and then no code ownership (and people were assigned tasks from different parts of code) for a few months. Then we went back to code owenrship. I think it was reasonable solution - better productivity, but people know more or less where to search for something, even if John isn't available when the bug hits. I particulary liked pair programming and would like it to happen every few months for a few days.