At SFO today the screeners were friendly despite the beginning of the end of week crush.

One guy calmly explained three times that "water is a liquid and so is hand cream" to a middle aged woman. I looked for a FlyerTalk tag. :-)

At DFW (had to transit security - long story) they were, as ever, excellent in the face of not enough room and too many people.

I personally would estimate the 'bad apple' ration a lot lower than 1%.