Google's search departments were for years organized by the type of content being indexed, i.e. Web Search, Image Search, Video Search, Product Search, Book Search, Blog Search, Discussion Search (RIP), Google News, Scholar, etc. For a long time these distinctions were apparent in the UI (they were de-emphasized after I left, which IMHO was a very good thing), but the differences go way down through the search stack, with different indexes, different ranking functions, and in some cases different ingestion mechanisms.

As for what happens when these become inadequate for the queries users ask...well, buy Metaweb and rebrand it as the Knowledge Graph. ;-)