the archives, but somehow Google found it, indexed it, and the guy threatened me with bloody murder if I didn't take it down.
Yes. It is critical to keep user perception in mind. Specifically, if you don't keep email addresses off the global search engines, there will be a deluge of vocal complaints from users who neither care about nor understand the technical aspects. That can be as simple as robots.txt configuration, or as fancy as using a captcha based system to reveal addresses like the one offered by reCaptcha. But my main point is you need to cover the user perception angle almost independtly from the core technical aspects of anti-harvesting.
For the record, I prefer keeping data as unadulterated as possible because it helps interoperability. But we also need to keep users happy.
-Jeff