It seems to me that if you're okay replacing ads on Gmail you'd be okay with replacing ads on Search as well?

Or are you saying you're okay with replacing ads on Gmail - but on Search replacing ads would be wrong? This seems like a slippery slope you're treading.

Like I said, I see the two business models very differently. My personal theory is that there is a LOT more potential revenue for Gmail in the enterprise. (Google tried and largely failed in the internal enterprise search market.)

Each small business of 20 people that pays for Premier service makes Google $1000. (And that's $1000/year recurring revenue.) Those same people would have to click on a LOT, LOT of ads (content/display ads, which earn much less money than search) to make the same amount of money through advertising. And there are hundreds of thousands of businesses world-wide that are potential Google Apps customers.

Fundamentally, I see a LOT more potential revenue for Gmail through enterprise deployment. If they have to sacrifice a small amount of ad revenue in order for users to use the tools they want to use as part of their job/life, then that's a tradeoff I'd be more than willing to make if I was in the shoes of a Gmail manager.

The model for Google web search involves getting as many users to search on Google, and putting the most relevant ads possible next to the results. The enterprise aspects of the business model don't exist, and that's why Gmail business model != Google search business model.