Governments, and in particular US one, are principal buyers of zero-day vulnerabilities according to a report published by Reuters. Zero-days exploits are considered a primary ingredient for success of a cyber attack. The US Government, in particular its intelligence agency and the DoD are spending so heavily for information on holes in commercial computer systems, and on exploits taking advantage of them, that they are turning the world of security research on its head, its a news way to compete with adversary in cyberspace.”]
Source: http://securityaffairs.co/wordpress/14561/malware/zero-day-market-governments-main-buyers.html