I have a domain — clockworkmind.com --- that I have an idea of using for development purposes, but I haven’t set anything up yet. In the meantime, I set all email messages coming to that domain to forward to my Gmail address.
Today, I received 200+ bounced messages from where a spammer used random usernames combined with [at]clockworkmind.com to send out spam to addresses that either didn’t exist or were blocked. There’s a great introduction to the world. :|