Doh. Dunno why people keep doing that. Thanks, GiantDomains... I'd asked this question before when someone else had sent out a mass e-mail to join a different forum. Didn't quite see how they'd go about harvesting, but that makes a lot of sense.
Somehow I don't think the owner of the forum NameCaster is a mod for would agree with that type behavior. Spam always seems to make the erroneous assumption that the sender is doing you a favor (and if you don't like it, just ignore it.) I've got thousands of "favors" in my inbox right now that I can't seem to find time to work through.
The worst culprits are the legions that insist "This is a ONE TIME mailing! You won't hear from me again if you are not interested."
More people should think twice.
~ Nexus