When someone with a feminine username joins your community, and you say “OMG a woman on the Internet,” or “jokingly” ask for naked pics, you are being an asshole. You are not being ironic. You are not cracking everyone up. You are the number one reason women are so rare on the Internet.
– http://geeketiquette.com/archives/2007/09/27/mad-props-to-xkcd/