I have had my personal email address for quite some time (5-digit UID and it's the same email address with which I registered my /. account, so 1998?). About a year ago, I got a reply to an Emily Wright. Luckily, the original email had her correct address (same as mine, but with a digit). Apparently, she goofed on setting up the reply-to in her email client.
Anyway, I forwarded her the email explaining the problem and giving pointers on how to fix the problem. Well, Emily replied and accused me of hacking her email account and flat out insisted that she owned my email address and had been using it for the past two years (or about a decade less than I've had the account).
My attitude went from "helpful technology capable guy" to "fuck you, you arrogant bitch". Now, anything addressed to Emily goes straight to the trash can, no matter how important it appears to be.