[josefresco]

This as an extension to AdWords doesn't seem like a horrible idea. For some retailers, allowing Google to complete an order might be a net improvement over their own store/experience. For the small to medium size etailers, Google most likely can offer superior experience and an "order is an order" assuming the net profit is reasonable.

[prophead]

Advertisers will also opt-in to using it as a way of differentiating their Ad from competitors.

Google and Advertisers have figured out that constant small changes to search Ads prevent "PPC Blindness" and every new extension gives a temporary incremental lift in regular ad clicks.

[josefresco]

Exactly, just the the click-to-call and other ad extensions. If the CAC goes down small to mid-size retailers won't care.