British investor Azeem Azhar, who has a strategy role at the startup search engine True Knowledge, notes that while it's useful to have a large base of knowledge, sometimes the sample that's selected matters more. "There are certain things that people expect to have, and there are certain facts that are more useful than others," he says. True Knowledge, which aims at the subset of searchers who are looking for answers to direct questions, is currently working on building up a database of relevant facts that can be used to answer questions such as, "Who was president when Barack Obama was a teenager?" The company hopes that by focusing on facts of broad interest, such as those relating to famous people and places, it will be useful to people even as it solicits responses for them by way of rounding out its database. When a user asks a question that the system can't answer, it returns, "If there are any answers, I couldn't find any"; invites the user to add to the database; and points to traditional search results.

Azhar also notes that it's hard to approach many common search problems directly. For example, while many companies are trying to improve search by parsing documents using natural-language processing or, like Cuil, analyzing them for context, True Knowledge is building a database containing facts and their relations to each other. "It's a testament to how difficult it is to improve automatic understanding of documents that we said we can build a database of several hundred million facts more easily," he says.

True Knowledge, which is still in a private experimental release, has no plans to go head to head against the majors. Azhar says that the company may eventually try to sell its services to existing portals as a feature that could enrich traditional search results.

That may be the safer approach. Positioning yourself as an alternative to Google, or, for that matter, to Microsoft's and Yahoo's search engines, is highly unlikely to be a viable strategy at this point, Sullivan says. "[Startups can] really underestimate the amount of work that's involved with the incredible task of trying to compete with Google." Instead, he adds, startup search engines might do better to present themselves as supplementing what the existing major search engines offer, or as providing good results for particular types of content.