If you do any online marketing for small local companies, or huge companies with thousands of local brick and mortar locations I suggest you hustle over to check out Which On-line Directories provide details to Google Maps.
In analysis Mike Blumenthal found that of 16 restaurants in Buffalo New York, 10 of them have data from Citysearch.com, 7 have data from RestaurantRow.com, and seven more again have data from Wcities.com.
He’s got 18 sources total listed in the post linked above (one of them is owner-submitted data), and there’s no mention if Yahoo, MSN or Ask Local use data from these sources.
Regarding ranking well, Mr. Blumenthal notes in Sources for Google Map’s Restaurant Local Listing data that “Local web references and the total number of reviews seem to have the most impact on your Maps ranking.”
My thoughts here are that you’ve got to roll up your sleeves and get links from your local Indie papers if possible (hire a PR firm for this and/or start some local charity work) and start incenting your local customers to review you in whatever relevant review sites exist for your area.
Mr. Blumenthal’s blog is a new one to me, but he’s done his homework here and provides a concerted look at online local, map-based marketing. Kudos!