My initial thoughts - Google Instant does not make sense. Google suggest was perfect, as it led people to potential search terms.
For those people who havent read about it, Google has launched a new service called Google Instant - where search results start popping up as the user types in their search terms. This is an extension of Suggest - where the search box, suggested keywords based on what users typed.
Use case 1. Type "a", and you will get Amazon, and you could be searching for any keyword that begins with a.
Problem for user: Hey, this is not what I want, do not disturb me as I type!
Problem for advertiser: Amazon ads will be shown to all people who search for a term that starts in "a". That's an exponential increase in impressions - wasted impressions. lower CTR, lower quality score.
And then, I may be completely wrong - only time will tell. :)