> The downsides are hypotheticals about the police potentially nabbing you based on an extreme ability to find out what you did, while the upsides involve current, actual, real stories about the police nabbing you by simply making up violations and then getting them to stick.
The problem is having a huge pile of incomplete evidence makes it easier to make up violations and get them to stick.
Illegitimate prosecutions are built on confirmation bias. The amount of false positive evidence against you is proportional to the amount of surveillance you're under. More government cameras only produce more false positive evidence against you. Meanwhile government cameras can't really help you because your public defender doesn't have the resources to look through the footage and regardless any strong evidence of your innocence will have been the victim of a camera malfunction which "isn't suspicious" because it "happens all the time."
The better solution is for citizens to carry cameras and to have strong laws protecting the right of citizens to record the police. That way the footage can't "disappear" as easily and the recordings are decentralized so you aren't making it easier to fabricate an illegitimate prosecution out of the biased selection of false positives from big data.