The 24 hour thing is a unique loop-hole in UK law (and UK law only as far as I am aware), that anything you borrow or download may be used legally for 24 hours for testing and demonstration perposes.

Also, if you are dead Dr. Unne (following on from the example) and people do break the law and distribute your materials, then (this is again in the UK) there is no-one to follow up the problem. As only the copyright holder may sue.

Another silly fact, if you die your heir gains your copyright.