Now, having been online since the 1992 I personally take issue with that assertion. Death threats, rape threats, vicious violent threats are not, in my experience, reserved for any one particular gender at all. I've been threatened with all manner of nasty ends from being anally raped to within an inch of my life, to being burned at the stake (amusingly enough when that happened I was trolling myself and posting provocative neo-Marxist arguments on a a message board full of rednecks).
Anyways, mentioning burning here is rather apt, as responding like that is called "flaming" when it happens, yet it seems now that the Observer has taken up the cause have decided that it's actually trolling, they note
The frequency of the violent online invective – or "trolling" – levelled at female commentators and columnists is now causing some of the best known names in journalism to hesitate before publishing their opinions.Now, I must apologise here for being pedantic, but telling someone online that you hope they "DIE, DIE, DIE. I HOPE YOU BURN IN HELL!" or "I HOPE YOU GET RAPED......... TWICE!" is not trolling. OK?
It's an easy mistake to make if you think the word "troll" refers to ugly creatures that live under bridges. However, what it actually refers to is a form of fishing where where you cast a line into the water baited with lure, a spinner perhaps, and you drag it along hoping to catch a fish stupid enough to bite.
It is a subtle art where you post to a forum, a message board, a newsgroup, a blog, with the distinct purpose of making that community bite back at you. Your target is not the writer alone but in fact everyone that reads your words.
A good troll is one where the community bite and have no idea they've been had (see "oh how I envy American students" for details, a troll that kept getting responses for a year); a bad troll is when it's blatantly obvious the words are designed to cause trouble (posting a derogatory comment about Mohammad to an Islamic forum for example) and that is called flaming. See here for the legendary Ultimate Flame.