I have done this for a couple decades and it works great. I have been able to confront businesses that have either sold or leaked or otherwise mishandled my information. They never admit to selling my info (this may change with recent laws), but it sends a message that their behavior will be seen. It is also a great way to nullify the source of spam that makes it past the regex filters. (S25R methodolgy)
True. As soon as we start receiving spams on an email address, we would know immediately which website has sold our email address.