wait you're scaring me why should I put tape on my webcam
Webcams can and have been used to spy on people by both hackers and governments. There are websites out there dedicated to “open” webcams, where photos and videos of people caught doing private/intimate things (changing, masturbating, having sex, etc) have been posted; there are even websites where people can tune in and watch through unsecured webcams live. Webcams (and mics) can also be used as surveillance tools by the government. Both of these groups can access your webcam and record you without you noticing, for example if your webcam usually has a light showing when activated, these people can disable that.
I am telling you now: this is not a conspiracy theory. This is not paranoia. I have seen evidence of both with my own eyes, and so have countless others I know. People can use webcams to watch you. Tape them up.