It’s fairly common knowledge within the SEO industry that many local search sites - including Yahoo and Google Local - use a mix of sources to both populate and enhance their local business listings.

There have been several high profile business partnerships between search engines, providers of business and consumer list data, and even some local media properties - I’m thinking of Yahoo’s on and off-again relationship with Bell South Yellow Pages, and Ask.com’s collaboration with CitySearch, to name two rather different examples.

Yet even when the logic of some of these deals seems straightforward enough - as it was with Yahoo’s use of YP listings for its local business directory - some or all parties may shift strategies radically, on a dime.

The entire field of local search is, after all, in its infancy, or more accurately in its terrible twos (or fours), and the big search engines and various vendors are still trying to figure out how to set up long term revenue streams from the various products they’re managing and developing, how to position & brand themselves in the current and future web environment, and how to deliver the search results that users are looking for.

One of the most opaque local search”platforms” - especially in terms of questions about source data and possible strategic alliances with source data providers - is Google Local, and by extension Google Maps. This recent post from a blog by Mike Blumenthal called “Understanding Google Maps and Yahoo Local” - Which On-line Directories provide details to Google Maps - offers some interesting observations and conjectures about the role of locally-targetted and locally-”value added” directories and other sites in determing Google Maps rankings.

Mr. Blumenthal chose to look at Google Maps listings for “restaurants” in Buffalo, NY for his short n’ sweet case study. Restaurants are obviously a particularly good candidate for this kind of research, as they stand much to gain (and possibly lose) from local search results, which these days are of course supplemented by user reviews, newspaper articles, maps, and more.

The conclusion Mr. Blumenthal reached is simple: the listing with the highest number of links and references from a set of local directories sits proudly at the top of Google Maps.

There is another key observation that Mr. Blumenthal makes about the local directories which appeared in backlink checks on the restaurants listed in Google Maps: they often had a strong hospitality focus: hotels, restaurants, etc.

Yep, this is our old friend ‘contextual relevancy’ once again, the same algorithmic flux capacitor which largely determines the value of incoming links, “quality score” in AdWords, and probably the types of potato chips available on your local grocery store shelves by this point.

There are a number of unresolved questions, but for me the takeaway here is that you should devote extra effort to finding and submitting your clients’s websites to *quality* local directories.

Finding these quality directories will require extensive searching of the target market in Google and elsewhere, and use of backlink stalking on top ranking sites in Maps/Local.

I predict that some directories and local resource sites will be PFI or even PPC (e.g.- Superpages), so it is important to figure out - looking forward 6 months or so - which of these pay-to-play directories and resource sites you really need your website listed in in order to stack up against the top performing sites in Google Maps & Local.