The NGA is "secretive" with its data for a couple of reasons:

1. Many of the platforms used to collect NGA's data are classified - and as such all the information they collect is also classified.
2. It is still very much illegal for intelligence agencies to spy on their own citizens.  There are (rightfully) a TON of legal hoops to get through before an agency like the NGA could collect and distribute data over the US.

In this case neither of those things happened.  What did happen is that NGA used a couple of its contract vehicles (Nextview and Clearview) to purchase commercial data from Digital Globe at rock bottom prices.  

These contract vehicles have been around for years, available to federal agencies for data acquisition and sharing between their State/Local/NGO partners.

It's great to see this capability being used at such a massive scale.