Indeed PT, I wasn't implying that it was Klez that did the "harvesting". As you say, ones' e-mail address can be gathered from many sources and one of the favourites is other folks' address books.
I also get spammed a lot by senders using the scattergun approach using incremental alphabetical variations. They're fiendishly cunning these Chinese (and Taiwanese, and Koreans and Ukranians and...)