It's a very long story, so I'll try to be as brief as possible.

A coworker made it very obvious she wanted to have sex with me. At first I didn't want to, but then against my better judgement I did. I told her later that it was a mistake and that I'd rather we just be friends.

She then wrote me a psychotic email about how she was so mad at me she wanted to hate fuck me, I guess thinking that I'd be into it. I told her that that freaked me out and that I was not at all interested in a hate fuck.

Within a few days she was terminated from the job for low performance, but that didn't stop her from following me as I walked home from work most days. She'd just show up and start talking to me, and I'd try to explain to her that I do not want a relationship, even a strictly-sexual one, and that given her recent behavior I didn't want a friendship either.

Then she started to appear in front of my house at random times, just as I was leaving. Or she'd just appear behind me on the subway platform.

She would go to the forums of the websites I worked at, and post personal details about me, embarrassing me in front of my colleagues.

This kind of behavior continued for about a year.

Eventually I started dating another woman, and I switched apartments. But I was incredibly careful about the move. I didn't even change my address on any official forms for the longest time because I didn't want my new address to be trace-able. But within a few days of being in the new place I got a hand-written invitation card with no return address that simply said 'DIE ALREADY' on the inside.

I called the police, and when they came to my apartment I showed them the card and told them the whole story, but they said that without any further evidence there was nothing they could do.

Eventually I moved again, across the country. I think she's finally stopped thinking about me.