I notice that the advent of the comment feature has greatly reduced the hate mail I used to get, except for the occasional knuckledragger who feels compelled to take issue with something on my user page or wants to challenge me to a fight....
A real fight, seriously....
The message goes something like: "You punk bitch can come get your ass kicked. I live in South Bug Stump, Tennessee and you can find me in the Pigs Knuckle Tavern every evening. I'll teach you a lesson you Yankee bastard."
Now, as oscar says, the hatemail usually comes in the comment feature. That makes it way easier to determine what someone's mad about.