ZDNet ran a story earlier this week about wireless spammers who drive up to open APs and send "millions of emails." They cited an expert, Adrian Wright.
Well, Danny did some research on this (i.e., he asked Adrian), and he discovered that Adrian had said no such thing — rather, he'd said that spammers could send spam this way.
My guess is that as long as you can send spam from home without having to put on pants, there's no reason why you'd go through this stupid business of wardriving open wireless nodes to use as a spam launchpad.
It's amazing how many people really want to believe that open wireless is/will be a scourge on the Internet, an enabler for terrorists and child pornographers and spammers — yet these same people utter nary a peep about the idea of libraries, Internet cafes, and kiosks in airports and conference centers that offer anonymous wireless access.