[marcos100]

If Google isn't useful then nobody will use it.

The search engine and the ads are tightly coupled. A better search engine means it can predict with more accuracy what you are looking for and can serve you an even more targeted ad that increases the chance you'll click.

[rchaud]

> If Google isn't useful then nobody will use it.

Or they'll continue to use it out of sheer inertia. Google is paying Apple $15 billion to keep its place as iOS default search engine.

IE6 didn't die overnight when Firefox arrived.