We have been engaged in scanning of the internet for its better health for over a year (we started with a few, then grew to a dozen). The decreases in abusable systems has dropped significantly in several areas. We have also had an inadvertent effect of identifying networking misconfiguration on many networks which has helped improve the stability and security of those organizations. Overall we have been very satisfied with the project and besides a few minor complaints it has been received very well by all of our consumers and the Internet in general.
more here............http://blog.shadowserver.org/2014/08/22/of-scannings-and-statistics/
more here............http://blog.shadowserver.org/2014/08/22/of-scannings-and-statistics/