If you're going to do electronic delivery of products, always use a valid reply address -- or verify the e-mail address before you ship.  Send a "click here to activate" link, send an account key, generate and send a one time password, w/e.

But if you're going to just blindly send, you might be sending to the wrong person.  If you send to the wrong person, they might not even speak the language that you speak.  Going to your website and struggling through a 20 part reply form written by your marketing department isn't a good experience, and you almost certainly want to know that you've delivered a password and a bunch of CD keys to the wrong person so that when your customer calls and says "WTF," you have an answer for them.

I filter tons of spam every day, but I still am going to maintain the support, parental guidance, etc. mailboxes at easily identifiable and easily contactable addresses.  I mean, it's just the right thing to do -- what spam gets by SpamAssassin and the other filters, we can deal with that.  So what there's an e-mail for viagra sitting in there.  If we keep just one, single, solitary customer because they can e-mail us, that's worth it. 

Been busy, haven't had the time to work on it, but we've had a couple more crashes and so this is moving up on the list a little.