Doesn't the TSA realize that this sort of thing undermines public confidence?
Inconsistent, bizarre regulations with secret rationales are NEVER going to go over well.

I remember when plastic cups were specifically permitted, but styrofoam was banned.

It seems like it all changes every day, so the lines are bound to be longer; it's almost impossible to prepare as a passenger if there is a shoe fetish one day, a cup obsession at the next airport, and cell phones at the other terminal.