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One of the things I've been meaning to do: look into pgp encryption. I've always thought about it mostly for email, and when I make my credit card payments online (because if there's a better place for encryption than when you move money from your checking acount to your credit card company, I can't think of one). I never thought about using it in a commenting system, however it makes a lot of sense. When you think of it like that, why isn't it worked into instant messenging, bulletin boards, etc? This is a good way to keep spammers out of your stuff too. Not authenticating yourself? I don't want your email then. I know it's kind of like whitelisting in a way, and there's a barrier for non-technical users, but it's definitely a topic that warrants discussion in my opinion.