Largest search engine in the world?

Answer 1

The world's largest search engine is by quite a long shot, Google. These figures are a little dated (April 2009) published by Comscore:

Google now has 64.2% (March 63.7%) of the market with 9.476 billion (March 9.125 bn) searches as against Yahoo! on 20.4% (March 20.5%) and Microsoft 8.2% (March 8.3%)

Clearly, Google with 64% against Yahoo! on 20% shows just what a dominant hold Google has over the search engines.

(P.S) - When you ask "largest" I assume you mean in terms of market share. "Cuil.com" claims that it has a larger indexed database than Google, but certainly is tiny in terms of market share compared to Google.