...as long as I'm thinking about icky things...
Within a year of the sig-changing incident, some spammer used one of my addresses in the From header of their mail. The address was one of those 'free for life' ones and forwarded to my less-permanent school-provided address.
I won't mention the provider of that address, as they may have cleaned up their act since then.
I discovered a gazillion bounce messages in my inbox one day, some of which included the bounced message... which was spam. My address was in the From header. I also discovered a large volume of venomous hate mail from folks who had received the spam. While I felt bad for them, I was feeling worse for myself.
At that point, I was happy to leave them. Sucky service sucks.
This was years ago. Hopefully they've invested in clues since then.