Everybody hates spam. Domainers hate spam because spammers often select catchy memorable domain names as the return address path for their spam. Of course those individuals don't actually own the domain names they are inserting in the spam .. You and I do.
If I got a nickel every time somebody threatened to call the FBI, CIA or Legion of Superheroes because of SPAM which I did not send, I would have a very big pile of nickels. It is far too easy for nefarious folks to send "forged return path" emails via automated mailer programs using email accounts and domain names they don't own..
Perhaps Yahoo's DKIM solution will make all our futures more hassle free. More arrests won't stop the Chinese, Indians and Russians from sending spam, so this is largely symbolic.