Well that leaves the real questions: what sites were the bots clicking ads on, who owns those sites and which ad networks were they using?
The odd thing is that either these sites are already very big, or there are others ways they are getting 5 billion ad impressions.
A list of these 202 websites would be informative. I guess a number of them could be fake, to throw the scent off?
[1] http://www.adweek.com/news/technology/meet-most-suspect-publ... [2] http://imgur.com/WHxmmHo