http://docs.unity3d.com/Documentation/ScriptReference/Collider.html

This page mentions "If you intend to move the collider around a lot it is recommended to also attach a kinematic rigidbody to it." From what I understand about the collider / rigidbody issue is that this is a far more critical issue than simply "If you intend to move the collider around a lot…" it is more "If you intend to move the collider at all…"