lol, yeah i think if you spend like $100 million buying masternodes you could possibly spy on maybe 3% of transactions, would actually cost more than that because there are not enough masternodes for sale, not even close. there are solutions to even that unlikely attack vector in the works as well. unlike some other anon coins dash is constantly innovating and evolving.
here is the chart with the mathematical probabilities of a attack like that...
http://imgur.com/WuooipA
https://docs.google.com/spreadsheets/d/1hZ4BWlRgOmWSL336oBHmk0Mcl9AzdS6v6XsEDKlc5PQ/edit#gid=57965184