Google Inc., starting from just a smart algorithm, has developed a totally new business model, has become in a few years the world leading search engine, has developed winning applications as Google Earth, Google Video, Google Maps, Gmail, and is enjoying a huge success. Google, starting from scratch, has won the challenge against a giant like Microsoft and against the previous search engine market leaders Yahoo, Lycos, Excite, and so on.

The key question is:
why the Business Model is a winning Business Model?

The answer is a complex one, and involves more factors. It’s a mix of smart decisions, excellent marketing strategy, great advisors, highly innovative and risky business model, and great products. 
But one big key reason why the Google Business Model won:

Google had – and still has – a simple, clean, clear, minimalistic user interface, no frills, just the logo and the search box – easy and fast to load. Unlike Google, the other search engines were more like generalistic portals, full of confusion, full of useless features and useless links, full of annoying banner ads, heavy and slow to load. Google had a clear understanding on psychology of perception, and how the interaction eye/brain works, while the bigger competitors didn’t.

Bottom line is: If the user visits a search engine, what he wants to get is simply that: just a search engine.

Sources:http://www.vertygoteam.com/google_marketing_strategy.php