In the US, the analogy would be if apps had tracking SDKs in them, that fingerprinted users across apps, in order to better target them for advertisements, and then the US government can pick up that data and do whatever they'd like with it.
I've never really thought about it before, but it would be pretty easy for a three-letter agency to set up an online advertising company for this purpose.
They start their own airlines (Air America, JANET, etc.), so starting an adtech company should be a walk in the park.