Author: Best way to deal with the issue is simply to filter out and trash all messages from that unique address and move on with your life. Done it many times myself.
If they subscribe to a service such as SendGrid, MailChimp, or the like you may be able to have their mail provider ban or warn them. Just check the headers and look up the sending server.
Readers: If you add a pattern of periods in your gmail account you will still receive the mail, but it becomes a fingerprint of the original receiving list (Of course this is limited by the length of your email handle, 2^(length-1) unique addresses are possible). You can also use yourname+tag@anygoogleappsdomain.com to achieve the same effect, but some overly strict (Read: invalid) mail parsers won't accept tagged addresses.