Should search engines introduce a tag of some sort that enables you to tell the spider not to index and not to use the content for ranking or relevancy purposes? Similar to the nofollow attribute for not counting links, and similar to AdSense Section Targeting, that enables you to specific which content is the relevant content for the AdSense spider to serve up relevant ads.
So why not a tag to tell the Web search spider what content is the content that should be indexed?
Well, right away, you can see how people may abuse it. But besides for that, there may be a way for search engines to deploy it safely.
Danny Sullivan says that Yahoo! had plans on introducing such a tag. But for some reason, has yet to do so. I believe they had plans on introducing something like it about a year ago.
Forum discussion at Search Engine Watch Forums.