Avoiding the blacklist
If you send out an email newsletter, you may have experienced the hassle of being blacklisted from an ISP or web service. The asymmetrical nature of spam makes this particularly painful--professional spammers don't mind being blacklisted, because they regularly switch identities. It's the good guys (and the amateur spammers) who get hassled.
Here's a lens that can help good guys navigate their way through the issue.