Two of the biggest brands in local search are partnering and they're using open APIs to do it. Citysearch is including sponsored ads from YP.com (Yellow Pages) in its CityGrid ad network (our CityGrid API profile). Additionally, Citysearch reviews show up across the YP.com website.
The New York Times explains the approach:
To re-insert itself in the middle of all things local, (Citysearch) has taken a somewhat counter-intuitive approach. Instead of counting on visits to its own site, it is distributing its content to dozens of other sites, and making money when people see ads on those sites.
Of course, these sorts of partnerships are common among companies. The difference here is that it uses Citysearch's API, so it's not just YP.com using Citysearch. It could be you.
For example, theSuggestr is a mashup that uses several local APIs (see them on our theSuggestr mashup profile), including Citysearch. The mashup uses reviews and other data, along with user ratings, to provide suggestions.
Local search and content--and ads placed against them--has long been a popular model, as the New York Times explains:
Local anything and everything--business and event listings, ratings and reviews, and real-time updates about events and friends' activities--has become the place to be for many Web companies, in part because online ads from local cafes or shops are a huge and untapped opportunity.
It's arguably more popular than ever now, most likely due to wider mobile internet use. Location-sharing and mobile coupon services are showing up as relevant local advertising options. And most services turn around and make their content available, as Citysearch has done, to developers.