[3dGrabber]

> If junk starts coming in, that address is blocked, and I stop doing business with that company (if I haven't already).

AND CALL them, if possible: “I’ve received marketing emails from your company recently, how is this possible, I’ve never signed up, yaddayadda… “

Generate some cost on their side.

[account42]

Support calls will probably cost you more than the company unless you value your time very little - most companis don't post numbers answered by anyone paid highly enough for this to have an impact. Instead, call them out publicly or mail/call a someone in a leadership position if you can find contact information.