This map shows the locations of 460 million pingable IP addresses identified between June and October 2012 by a benign botnet called Carna:
My first reaction -- wow that is cool -- I like global visualizations of the world and the Internet -- check out the hot spots in Silicon Valley, Southern California, back east and in Asia. Look at India and China.
My second reaction -- aren't botnets evil?
Not this one. Follow the link above and you will find a full description of this ethical, benign botnet. It gathered interesting information and did no harm.
This map is only one Carna botnet result. For example it found 141 Million firewalled IP addresses and 729 million more with reverse DNS records for a total of 1.3 Billion used IP addresses.
Another example -- Carna counted the number of hosts in each top-level domain -- here are the top 20:
Internet Systems Consortium survey, which they have run since the beginning of the domain name system. For you old folks -- ISC used to be called "Network Wizards.")
You can see all that and more in the Carna paper, and all the data is available for download.
The author does not identify him/herself for reasons of modesty and perhaps fear of upsetting people, but, whoever you are, thanks for your effort and it would be great if you would it on a regular basis.