Word of a growing partnership between police and the popular Amazon-owned doorbell camera company Ring is raising privacy concerns nationwide. Ring's "Neighbors" app lets customers know when and where a crime happens in their area. It works in conjunction with the so-called "Neighbors Portal," which Ring said Wednesday is now used by some 400 law enforcement agencies to request customer video. That might help their investigations.

"My goal would be to have every law enforcement agency on the police portal," Ring CEO Jamie Siminoff said. "It helps all communities come together to make things safer."

Andrew Ferguson, author of "The Rise of Big Data Policing," said there's a downside, though.

"We're going to see a growing sense of people sort of becoming informants on our neighbors and our neighborhoods," Ferguson said. "And there's obviously going to be potential problems with who gets targeted in those neighborhood apps. And that can be very troubling because what could happen, of course, is there could be a police response. And that could impact someone's liberty, someone's lives."

Ring says its customers have "complete control" of their videos and can "choose to give consent to a law enforcement request" for access.

"The Ring customer will see a request come up, they can either accept the request or they can opt out of that request," Siminoff said. "And all future requests. And the police will never see if they have done that."

But privacy advocates worry that customers might not always have the final say.

"Yes, we have a choice, sometimes," Ferguson said. "But it's very easy for police to get a search warrant for that same footage if they believe a crime has occurred."

"I can tell you we will always follow the laws, but we will always fight for our customer's rights, their control and their privacy," Siminoff said.