
Google did that already. Copiepresse went to court to MAKE google put them on the search engine site (loss of visitors). Copiepresse have been told they can
a) use a robots.txt to stop spiders
b) use a HTTP tag to stop retention of pages
c) add a google-specific tag to their website to tell Google to stop caching
d) mail Google about pages they don't want cached
but Copiepresse didn't like ANY of these solutions. They wanted Google to sign to a copyright license to cache their stuff, pay for the license and not be able to decide NOT to agree (by telling the court that if Google didn't cache their site, they were interfering with Copiepresse's business and abusing their search engine monopoly).
Read up on the history of this, people. Groklaw still has quite a lot on it. Be considerate of their bandwidth.