[pm215]

If you don't have any results for the query, then return a page saying so. Otherwise you're annoying the user by making them scan through a page of irrelevant text to confirm that it really is all irrelevant. When this happens to me my reaction is "don't just ignore what I said to you", which is as infuriating when a computer does it as when a human does.

[jonbarker]

Google returns results specifically showing which terms were missing if this were the case for me. This is useful for finding articles with intersections of concepts (assuming I got the terminology/jargon right) and knowing when those probably don't exist, so I like the feature.