[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.