From the article cited earlier:
Citing threats of terrorism, the court ruled passengers give up all rights to be free of warrantless searches once a "passenger places hand luggage on a conveyor belt for inspection" or "passes though a magnetometer."
So, theoretically, if I'm not carrying any luggage that goes through the X-ray and I step through a NoS instead of a WTMD, I haven't waived my right to be free of warrantless searches. Someone should try that out.