Turns out you can add anyone's number -- or remove anyone's number -- to/from the Canadian do-not-call list. You can also add (but not remove) numbers to the U.S. do-not-call list, though only up to three at a time, and you have to provide a valid e-mail address to confirm the addition.

Here's my idea. If you're a company, add every one of your customers to the list. That way, none of your competitors will be able to cold call them.