That is where I differ from most on this subject. I do not worry about their ranking or what Google does or does not do with them. I learned a long time ago that it doesn't pay to dwell on things you have no control over.
My only "complaint" is the amount of ignorance shown by those that are doing it. After that, it is up to me as a site owner is to protect my own sites and the content they contain. No different than WebmasterWorld does by not allowing others to take the threads/content and post it on their sites.