I have a couple of aftermarket amplifiers in my car. I spend a lot of time in it, so felt it was worth the effort needed to improve the audio system.
Both amps have a dedicated lead running to the battery (each with an appropriately rated fuse just after the battery), though they share a ground point (to minimise the potential between them and avoid ground loop noises).
From that description, all should be good and safe right? Wrong. Luckily I caught it before it developed into anything more serious, but this post is to demonstrate why it's important not to let yourself get complacent. Check your wiring regularly.