Ego

Media attention often is a major motivation behind a worm. Coders bolstering their ego by seeing reports on their worm on major sites on the internet as well as tv news and newspapers with paniced warnings of the latest doomsday threat which may take down the planet and result in a 'Digital Pearl Harbor' seems to be quite often the case. Huge media attention usually also means huge law enforcement attention, and big efforts will be made to catch the perpetrator. Though especially wide open (public) WIFI networks can make it quite difficult to catch the perpetrator by technological means, people boasting on IRC and, as in the case of Sasser, bounties, can quickly result in the worm's author being taken into custody.