We are getting ready to implement a feature on our site that would create massive duplicate content. It is good for users, bad for spiders. We have weighed several options about how to avoid this.
1) rel="canonical" - I think this is not the best option because it will still allow spiders to use up our resources
2) block all major bot User Agents from seeing this feature - Would require updating, would never be able to block all bots.
3) Meta noindex, nofollow, noarchive - Could be a possible solution
What do you guys suggest/had the best luck with?