I've been going through some change-of-mail-address exercises lately, moving some subscriptions away from an account I'm not using any more to one I set up on gmail specifically for subscriptions.
I'm amazed at how many of these lists include links to unsubscribe (as they should!) but many don't have links to change the address. It's unsubscribe or nothing. What's even more amazing is how many of them are vendors of email marketing solutions and advice.
As an experiment, I'm tweeting the publishers to see if they are actively managing their twitter accounts (more on that later.) If I don't hear back from them, it's 86 for them.
Moral of the story: People change email accounts, especially when they change jobs. Make it one-click easy for people to change their address with you, or risk losing them.