This is big news -- bigger, I think, than Google's recent increasing emphasis on video.
Direct marketing, online and off, represents the tip of the ad spend iceberg. Most products aren't shipped to the home. Most products are bought in local stores. Most services are delivered locally.
Being able to show the benefit of an online ad pushing sales into a store is huge -- a holy grail of response advertising. Right now, few large store chains with direct marketing arms (ditto, few large direct marketers with store networks), have the capability to distribute coupons online for store redemption, and fewer have well-integrated systems to track redemption of online coupons at store POS systems.
I suspect with this release, the small business owners may be able to sieze this grail before larger companies...
Local business owners know when coupons work or not -- they're often at the cash register themselves, and can see the coupons come in, or not -- and they know what they've spent on those coupons, discount and distribution included. Small business are often many times nimbler than large corporations. I think Google Local Coupons could see broad adoption over the next year, stealing even more share from print Yellow Pages.