I tend to agree with John Gruber’s thoughts on “On Covering Webcams”
The problem isn’t your camera, it’s malware. Don’t install any software from unknown or sketchy sources, keep your OS up to date1, and you should be fine. And if you do have malware on your Mac, the webcam is likely the least of your problems.
Sure, you should be careful while you access the Internet. Or else some can indeed take control of your machine. But the words I highlighted matter — you should be careful while accessing any machine. Else, you will break the machine and it will eventually harm you.