There is some interesting commentary at
Mike's blog on this topic.
Bill Slawski referenced one of the google patents he wrote about. Also
Will Scott provided some quick analysis of
seo factors that might have created the situation.
It certainly appears the florist with the onebox, Lehrer's has had a lot of
seo work to obtain the map. His site is ranked 2nd in the organic
serps for
denver flowers behind the denver flowers site and store itself.
In fact looking at the data Will provided it looks like an overwhelming amt of
seo work had more impact in map algo and onebox results than in organic
serps. (I'd say title tags REALLY mean a lot in organic
serps)
Further analysis shows that within Google maps itself; a search for
denver flowers places lehrer's 2nd behind a florist shop in a hotel.
Of interest, the hotel florist is the closest to the city center for Denver (as determined by navteq-google's mapping partner). But regardless it is Lehrer's who shows on the dominant map insert into organic results.
The letters from the denver florist really point to the power of maps when inserted into organic search. When it becomes this type of "authoritative map it really impacts business!!!!! It absolutely dominates the visual real estate of the search page.