Copyright notices (or the lack thereof) in kernel code

The US comes surprisingly close. Commercial copyright infringement is technically a criminal matter, but in practice the federal government has better things to do, so you would usually only get prosecuted if you make a nuisance of yourself and the (rather substantial) civil remedies are inadequate. See for example Kim Dotcom. But the vast majority of copyright infringement is either handled civilly or informally (i.e. without directly involving the court system, usually in the form of DMCA notices, as well as stuff like ContentID).