> A dragnet being an indiscriminate stop and search...

Nope. You need not stop everyone -or even anyone!- you search for it to be a dragnet search.

A search that is widespread and indiscriminate is a dragnet search... regardless of whether it's done by agents of the government or by the private sector. [0]

The thing being caught in the dragnet is not people, but information about with whom those people caught in the dragnet associate, where they spend their time, and other details about their private lives that -frankly- the government has no business knowing without either paying the cost to have a police follow those surveilled around, or justifying beginning and continuing the search of specific individuals to a court and receiving its approval.

[0] I'd love for the courts to start generally taking notice of the fact that a private sector company for whom the overwhelming majority of its customers are public-sector law enforcement is very likely to be defacto acting as an agent of the state. Private companies acting as agents of the state have far more strict regulations that apply to them, and it'd be really good for courts to catch up with the current situation on the ground regarding the public sector's "partnerships" with private-sector companies like Flock, Axon, and similar.