And you'd never even know they're there.
By now you've almost certainly heard about that high school in Pennsylvania that got in trouble for issuing its students laptops, and then spying on them in their bedrooms, remotely, by controlling their webcams.
We're going to bet that, before that story broke, you didn't know there was even such a thing as turning on somebody else's webcam against their will from across town. And maybe you thought the school had done some weird modification to the laptops, and that it was just an isolated incident by a somewhat insane school district.
Class outside? What the f**k is going on here?
The truth is, it took basically no effort on their part. All sorts of programs are available to let you remotely commandeer a webcam, and many of them are free. Simple versions will just take photos or videos when they detect movement, but more complex software will send you an e-mail when the computer you've installed the program on is in use, so you can immediately login and control the webcam without the hassle of having to stare at an empty room until the person you're stalking shows up. Convenient!
Leaving creeps free time to work on their Harry Potter/Starfox slash fiction.