According to Webcam Watcher's site your webcam must be added to their list and categorized before it can be viewed by the program.
In order to activate someone's webcam that is turned off, you would need software access to their computer and webcam, and all means of doing this are absolutely illegal (Trojans etc...)
You may be able to access a webcam that is turned on, through yahoo or msn or some such thing, without a person's knowledge, but this particular program has no means of doing that.
So, for the one who posted the thread, as far as using that program to see you on your cam, it is 100% impossible unless you have added your cam to their list.
edit: read CBrewton5 's reply (Frenchee!
) and I agree that's probably it, just leaving this up to put people's minds at ease