I wouldnt call it good. This is criminals stealing from other criminals, which is still crime. Just as how gangland wars can impact innocent bystanders, these nested layers of illegality and theft of information can cause harm to others.
https://www.aclu.org/issues/criminal-law-reform/reforming-po...
Not often enough, apparently. Not always "criminals". Just suspects...
Criminals do get charged with theft from other criminals. The only benefit to stealing from criminals is that they won't go to the police, but that doesn't mean they won't report you once they get caught. They may even get out if jail earlier by coming clean and listing every criminal they've interacted with.