This is potentially a real risk to Google. The odds of such a huge success it decreases Google's profits are tiny (I think). But there is a real risk that the

This is potentially a real risk to Google. The odds of such a huge success it decreases Google's profits are tiny (I think). But there is a real risk that the increase in Google's profits going forward are materially affected by a well done competitor to Adsense. If Amazon took away 10% of what Google's adsense business 4 years from now would have been that is likely material to Google's earning. Not huge but real. Even losing the ads on Amazon's web site is likely noticeable (though not a huge deal I would guess). There is even the potential Google has to reduce their profitability to compete - giving web sites a better cut of revenue. That said I think Amazon has plenty of challenges to making it an effective competitor to Google. But they have a chance. And there is even a small chance (very small I think) that Amazon could create a competitor that actually results in noticeably (say over 15%) declining revenue to Google via adsense. Likely even in this case Google continues to grow profit. Google revenue from ads from their own websites are the most important earnings and likely to continue to be so. Also new business (non web-ad-income) is growing and I think will continue to do so (this is likely an area some might find more questionable).