http://theviewfromhell.blogspot.com/2012/09/toward-non-stupid-non-blank-slatey.html
The author gives a shout out to Less Wrong as a community with a perpetually skewed gender ratio, which is precisely the conditions under which polyandry appears to thrive.
Discuss. :)
Changed it to link to the Google Books result for "cuckold" within the Billion Wicked Thoughts book: http://books.google.com/books?id=jwU8_m8y5X0C&q=cuckold#v=snippet&q=cuckold&f=false
As far as I know, the book is the only place the data are reported, sadly. I agree, it's juicy if true!