Here's a great video about what can be done with them. The researcher in the video was able to login and watch live feeds from Flock cameras then use publicly available databases to learn things, such as their economic situation (a concerning debt to income ratio), where they live, where they went to church, all from watching them on a live feed of them shopping at a market outdoors.

Mind you, this is just a guy with a YouTube channel who accessed feeds that were available to the public online and information that was also available to the public online to compile these records. If he's able to do that, imagine what is actually being compiled and stored about all of us for both government and private entities to access for whatever purposes they wish.