Microsoft Search, Ask Us Anything

We have two high-level goals that we'd like to achieve. We'd like to give people short, succinct, targeted results directly related to the topic they're searching on. We'd also like to make sure that we index a broad, comprehensive range of materials (everything?) in order to support discovery, learning, cross-silo collaboration, and generally to take advantage of that big data set. People like short lists of results, but they don't want things to be left out. People like long lists of results, but they don't want to be overwhelmed. What's the best strategy for balancing these two approaches in the MS Search ecosystem, the narrow approach and the broad approach?