Since I own various .com domain names, I have my email set up to deliver all messages sent to one of them into a single inbox. Today I received a Twitter invitation from someone I don't know, sent to a fake address. This didn't mean much to me until I thought for a minute what that meant.
Those Twitter invitations are sent out when someone signs into Twitter and gives Twitter their email login info so that Twitter can spam everyone in their contact list. (I still don't know why someone would willingly do this.) Since it was a fake address, this means that she must have gotten it from spammers, who like to use random strings of characters @ some domain name they don't own as the "From" address of their mail. And since a Twitter invitation went out, that means that she added a spammer's email address to her contact list. Not only did she respond to that spam, but also that she was like "I think I'll want to remember this address for later."