If this really were the doctrine under which these searches were instituted, wouldn't there have to be a situation where the search procedures are fixed at the point where you bought your ticket, and they can't spring surprises on you by changing procedures between purchase and travel? Maybe I'm being unreasonable, but if the idea is that you implicitly consent when you sign up, then it seems like they should not then be able to change what you consented to later.
Exactly that? Consent isn't what enables the search, but it's still good that the TSA can't raid your house. What enables the search is (i) no investigative intent and (ii) no discretion on the part of the searchers as to who to search.
