The second saddest part of the story is that the person responsible for securing the biggest DWH of all time freely admits that they have no protection against rogue sysadmins, most of whom don't even work for the NSA.
If Snowden was the first to leak information, who was the first to sell it? The way Snowden describes the access seems like a joke.
If anything, a contractor is going to have additional vetting. As an employer, the federal government is bound by constitutional restrictions that private employers are not. For example suspicion-less drug testing is not a requirement for a clearance (affirmation that you haven't used illegal drugs is a requirement, but actual testing is not). However most private employers are all gung-ho on the drug testing front and do force employees to be tested to whatever level their local state laws permit (there is significant variance by state as to what a private employer can require).
A government employee might be getting paid by a third party whose interest diverge from the government's.
A government contractor is, by definition, getting paid by a third party whose interest diverge from the government's.
Whistleblowing, sure, generally. Espionage on behalf of a foreign power, probably; espionage on behalf of the company itself... heck, government contractors in non-security related fields not-infrequently expend considerable effort to gather non-public information about their current and potential employers and competitors.
Even then it isn't quite espionage that's the problem but simply working to steer more business their way - inside information on operations feeds into the lobbying arm of the contractor and the lobbyists convince congress to create or expand the work available for which the contractor has a high probability of winning the bid.