The natives are getting restless, and chatty, and so it's time for new seating charts. I used to feel semi-bad about moving them around and deciding where they sit, but now I don't. As I tell them
1. it's not fair to always have to sit in the back/front/etc for the whole year
2. it's nice to meet new people
I poll them on quarter sheets of colored paper before I switch seats, to see if they have issues (eyesight/air conditioner/strong dislikes...), and to see how everything else is going in class and in life. I've gotten various positive comments back about seating charts, and I've noticed students actually making new friends after seats have been changed, so I guess it's a good thing ... AND quiet for a while.
And if I remember, the first day after seats are changed, I make sure to put 2 questions on the overhead for them to discuss with their new group (they sit in groups of 4 seats) for about 5 minutes, and then we class share, so that they get a chance to be forced to interact and learn each others' names.