Did someone invent this because a woman died in a public loo after becoming paranoid that someone might be outside waiting to jump her as she opened the door and so never did, or are all the people in Houston wannabe exhibitionists that go in there to practice?
Don't see why Kev.
These things are very strange. Some large London underground stations used to have them in their control rooms that looked out across the concourse so the controllers could see if the escalators were getting overcrowded. I was shown round one once. People would come up and check their hair, ties, teeth and worse in the mirror completely oblivious to you looking back at them a few feet away.
As far as I know, the darker side can see the lighter side, but not the other way around. However if it's lighter in the loo, than outside (e.g. at night), I think you'd be able to see in... Only time I was in a room with a two way mirror, the viewing/secret area was kept dark when in use. When I was in the observation area, I could make out what was on the other side, cos the lights were on there.
Interesting Kev. I wonder of the technology has changed. My experience was a good few years ago. I recall the lighting was much the same both sides. However the reflecting side was not not a plane surface - as in the Houston loo - but had a kind of vertical stripey effect. Some people looked at it a bit oddly at first, but most were in a hurry to catch a train or leave the station and didn't stop for more than monent or two. I suspect that CCTV has superceded it on the underground now anyway, as I was recently at one of the stations that used to use it and it was no longer there.