Lazy guy that I am, I installed "touch switches" in the bases of four metal bodied table lamps in our home.
It's a heck of a lot easier to just reach out and tap the lamps than to have to stretch and reach up under the lampshades to twist the typical socket switch knob. And, they provide four levels of illumination from an ordinary bulb.
I might add that shortly after I installed those switches about 15 years ago I learned the hard way that I had to install a fuse holder with a 2 amp fast blow 3AG fuse in the line going to the lamp bulb because when a bulb burned out sometimes a "tungsten arc" occurred and drew a surge of current large enough to fry the touch switch's electronics. Now, I only have to replace a 20 cent fuse along with the lamp bulb.
SWMBO and I were sitting on the sofa watching the November 2nd election returns when the lamp on the end table next to me turned off. I thought WTF? and touched the lamp which turned it on again. I went back to watching TV and a few minutes later the lamp turned off again.
I figured maybe the lamp bulb might have gotten loose in its socket or the lampshade loose on its stud and stood up to see if that was the cause.
When I looked down into the lamp shade I saw a ladybug crawling on the lamp socket. A few ladybugs join our family every fall, seeking warmth I guess.
I stood there and watched as that ladybug crawled up the side of the lamp socket shell and started to walk around the neck of the bulb.
The moment its legs touched both the lamp socket shell and the side of the bulb's screw base the lamp went out.
Mystery solved. The bug was creating a connection between the lamp body and the bulb's screw base (Said base was connected to one side or the other of the 120 volt line). That connection drew enough current out of the touch switch's sensing lead to cause it to react as if someone had touched the lamp and drawn enough capacitive charging current to activate it.
Who woulda thought it? I kicked that ladybug outdoors again.
Jeff