As someone who works at a company that sends a lot of email, we naturally have ways to opt out and to remove yourselves from our mailing lists. There is a BIG DIFFERENCE between removing yourself from the list or unselecting preferences than doing the CAN-SPAM opt out.
IF YOU CAN AVOID IT - JUST UNSUBSCRIBE YOURSELF.
When you do the can-spam opt-out-never-mail-me-again, we're required to keep it on file. We're also required to send this list of email addresses to every agency that markets for us saying they're not allowed to contact you on our behalf.
Now, I want you to read that last paragraph again. They're not allowed to contact you on our behalf, but they can (and almost always will) send other mails to those accounts. This means, through no fault of their own, the place you're opting out from has just given your valid email address to a bunch of other marketing firms.
Now, we have agreements in place with all these other firms that market with us, yadda yadda, and we seed them with dummy addresses so we know who has used our list of opt-outs to spam folks - but the reality is that the damage once it is done is done. and once that list goes out once it goes out 1000 times.
So, do yourself a favor, filter your mail, don't use the don't contact me again ever opt-outs, but unsubscribe if you want. It really sucks, but the law actually makes it easier to spam you rather than harder.