A WebmasterWorld thread shows that a Belgian court has ruled that the Google Cache and Google News is in violation of "particular the laws on copyright and ancillary rights (1994) and the law on data bases (1998)." Google has to remove "the articles, photographs and graphic representations of Belgian publishers of the French - and German-speaking daily press" or pay a daily fine of 1,000,000.- €.
The full details are at Chilling Effects.org.
So Belgium will require an opt in for caching, should the rest of the world?
Forum discussion at WebmasterWorld.