Every now and then I get an email from someone announcing that they've got a new email address. Invariably, they send this email from their OLD address. I never maintain an address book in my mail client. Rather, when I write to people I either type in the address (if I remember it), rely on auto-complete or search for old messages and “reply” to them. So, unless I am careful, I am likely to later “reply” to the old address, since this is the address the message came from. Why not send the message from your NEW address so that all recipients would immediately have it in their mail clients.
Another thing: why do people give out multiple email addresses. How am I supposed to decide which one to use? Why can’t the person just decide where they want to get their mail and give me that ONE address?