Hiding specific content from search engines (NOT an entire 'page'). Is it possible?

Hi all,

We're considering migrating an existing social application to Drupal, and will be including a user forum in the new site. We would like individual users to have control over the privacy of the information they contribute to the forum: Some would like their forum posts to be indexed by search engines, others may decide they would like to hide a specific forum post from spiders. We are trying to avoid a global ("one size fits all") approach to privacy.

Is this possible??