From what I gather it occours when your steering linkage is out of alignment due to a lift kit or bent drag link. This causes a push and pull effect in your linkage when your suspension moves up and down, causing the wheels to turn slightly whenever you hit a bump. A lift causes the drag link to go out of paralell with the tie rod. The only way i know to correct it is to replace the pitman arm with a longer or "dropped" pitman arm. A bent drag like will cause the same problem but its usually less noticable.
1992 YJ, 2.5L 4-banger, 2" Lift, 31x10.5 BFG Mud Terrain, K&N Filter, Restrictor Removed, Hi-Lift, Custom bumpers, More to come...