Spam is commercial, unsolicited, unanticipated, irrelevant messaging, sent in bulk. It's the email you didn't ask to get, the junk in the comments that's selfish and trying to sell something, the robocall on your cell phone from a company pretending to be Google Maps.
Some spammers will tell you that all you need to do is opt out. But of course, the very problem with spam is that it requires action on the part of the recipient, action that can't possibly scale (how many times a day should we have to opt out, communicating with businesses we never asked to hear from in the first place?) People are smart enough to see that once spam becomes professionally and socially acceptable, all open systems fall apart.
Spam is in the eye of the beholder, and so my definition of permission marketing kicks in: If the person you're communicating with would have missed you if you didn't show up, you have permission. On the other hand, just because you know someone's email address or phone number, just because you have figured out how to automate a captcha or hack a discussion board doesn't mean you're welcome there.
What to say to the business person who says, "sure, that's fine, but how do you get permission in the first place? How can I get noticed without spamming people to get started?" The two answers: 1. spend some cash and buy socially acceptable, scalable announcements called advertising. Or 2. Tell ten people.
It's easy to count how many sales you created by spamming a list. Harder, but more important, to count how many people you burned all trust with.
Trust, as we know, is the essence of connection and transaction, and spam is the radioactive antitrust device.