I think that the double opt in policy should be absolutely mandatory for anyone who signs up for anything by email. Plus, I think that if you get someone using your email address trying to sign you up for stuff, that when you get the opt in email there should be a way to report illegal use of your email address. Then the company should be responsible for tracing the sender’s IP. There should be an option to reject all incoming mail from a domain without just redirecting it to a spam folder. Reporting spam in email needs to go to the next level now.
If someone does not like you, they can sign you up for all kinds of stuff just using your email address. Of course in most cases you have to click on the first contact email to finish the signup process. However, if you have a stalker or someone trying to just pester you, they can keep signing you up. Then you keep getting those first contact emails. You know the ones. They say something about how your email address was used to sign up for a list, and that you have to click a link to confirm. If you do not click, you do not get any more emails. However, you can get at least one from every domain out there that has a sign up option. Then they can do it again later on using the same places.
If they have your work email address, an administrator may question why you are getting emails from restricted domains. It can cause you a lot of problems and even a trip down to the Human Resources office. I think that email is to easy to use to cause problems. If it has never happened to you, then you are fortunate. Some people are inundated with bad spam emails because someone thinks it is funny or wants to wreak havoc in their lives.