The bigger issue with these pat downs, scans, fluid limits, etc is whether they're effective.
Bruce Schneier has written at great length (and very smartly) about this stuff. And I agree with him that the single most effective deterrent to the next 9/11 is secure cockpit doors, and a close second is passengers not willing to "allow" a plane to get hijacked anymore (whereas hijackings in the past had a sliver of hope that you'd get out safely, after 9/11 I think passengers know there might be certain death, so why not fight?)