Caught this interesting video recently. Does anybody on the site have these bulbs?
https://www.youtube.com/watch?v=1uEmX5XClPY

On quite a few places I'm even adding a capacitor to make a kind of "nightlight" function out of it. Pretty handy when you have to go at night, you do not have to wake yourself fully up by a bright light when on the way there or when you need a sip of water... Consumes less than 100mW per room, so on the electricity bill not visible at all...
Of course only outside bedrooms...

Good demonstration but not accurate!, nobody has 100 metres of T+E to any switch in the average UK home!
There’s probably 5 or 6 metres at best, even in a large room?
And as Medved says, it probably makes a cool nightlight when it is just using the ‘stored electrons’ in the cable?

It can happens with all sort of bulbs.
It happended also to me with an old installation and a CFL: cfl started to flash randomly after turning off.
This was caused by the combination of:
- humidity
- old cabling (with rigid copper)
- old porcelain switch

Relative high leakage current caused cfl capacitor to charge and, after a certain voltage threshold, tried to start CFL which drained capacitor and the cycle repeated itself every 5-10 seconds.