SearchEngineWatch has an article by Greg Sterling about the US market:
Despite the fact that the quality of local search results is still very mixed, local search is clearly gaining traction with users.
The other side of local search, of course, is geo-targeted advertising. And the biggest potential market is small business. The U.S. has roughly 10 million small businesses, the majority of which have fewer than nine employees and conduct most of their business within 50 miles of their physical locations.
To achieve any sizeable revenues from the local market, paid search needs to gain small business advertiser adoption. But how much of the small business market will pay-per-click (PPC) be able to penetrate? There are some very practical challenges, which include:
The complexity and time involved in keyword bid-campaign management
Limited ad inventory and competition between national and small business advertisers for that inventory
The absence of local sales channels to “push” PPC to small business advertisers
The lack of websites among as much as 70% of small businesses
These are not insurmountable by any means, though they should not be minimized. It’s also important to point out that many small businesses are currently users of paid search advertising. But for the great majority of small business, there may be considerable ignorance and even skepticism about PPC.