I encounter these all the time and remember a time when I first started out where I got zapped pretty bad in the head from a broken light bulb that was still energized.
Keep an eye out for these things when you are entering into a confined space or have to duck under something to move around. One of these buggers may be lurking on the other side when you go to put your head up.
I used to wear a hardhat or bump cap when ever I went into an attic or crawlspace because of this. I am going to have to get back into the practice because I am encountering more and more of these for some reason.