Top 4 Things To Never Do To Your Users

The only good reason for this is it helps prevent people from signing up other people to harass them. But even then, most sites I've seen aren't smart enough to require confirmation to change the email address once registered so it does no good.

Companies should just offer RSS feeds for people who really want junk solicitations.

Really, who does this? Might as well remind us to register domain names instead of using IP addresses.