Several abilities available to monsters or PC's have the trigger "Whenever a creature moves willingly...", for example, "Until the end of your next turn, whenever the target willingly moves to a square further away from you, it takes 1d6 + Intelligence modifier force and lightning damage."
Some powers with the Fear keyword force a creature to, for example, "move its speed in the most direct way from the attacker" or "move its speed away, using the path of least harm".
This is not forced movement, but does it count as the creature "moving willingly"?