I found roughly the same thing comparing apache logs with google analytics.
A direct conspiracy would be a pretty bad business model, but fake friend and spam disseminating accounts may be less likely to be canceled if bots or minions keep them active with bogus activity.
If ~80% of profits is really from bots, then it's hard for fb not to turn a blind eye to these accounts.
http://techcrunch.com/2012/07/30/startup-claims-80-of-its-fa...
http://news.ycombinator.com/item?id=4312731
(The original link from the HN submission is unfortunately gone)