Three Letter Agencies don't have to DDOS. They just send in the heavies. It's cheaper.
And there have been voices high up in the government saying that the US needs to develop offensive cyberwarfare capability. If that's not a call to develop state-owned botnets... the people in charge don't understand technology.
Of course, the use of the term cyberwarfare might be a giveaway anyway.
In any case, I'm sure it's a pretty simple matter for some people in the CIA to quietly hire out a botnet.