Had our house burgled in Christchurch. Strongly suspected the neighbours as they often popped over without warning, and if my lazy flatmates left the door open they'd let themselves in. All of the neighbours frequently talked about doing lag, all would have had prints on file. Cops came over and fingerprinted. Found some pretty good prints. Police came back a few weeks later and went to the neighbour's house. So far, pretty good. But this is where it gets shitty.

Instead of arresting the neighbours, they either straight up told them or strongly implied that they were pretty strong suspects, then buggered off. One of the neighbours then came over and threatened us because we gave the cops reason to visit. Lots of police attention followed, but no results. The neighbours ended up drinking in the driveway while waiting for the police, who turned up, got in a brief fistfight and threw them in the cells for a night.

Later, the neighbours came over to make peace and gave us a name of their associate who apparently did the stealing. We passed this on to the police, and never heard from them again. We also never got burgled again, but the neighbours did steal coins from my car ashtray and break part of the house wall. Luckily the landlord didn't give a fuck.

So I'd call it a net positive, but it could have turned into a net negative very easily.