Unless the power of attorney has been made irrevocable by its own terms or by some legal principle, the grantor may revoke the power of attorney by telling the attorney-in-fact it is revoked. However, if the principal does not inform third parties and it is reasonable for the third parties to rely upon the power of attorney being in force, the principal might still be bound by the acts of the agent, though the agent may also be liable for such unauthorized acts.