I wasn’t aware of this before . . . YPG in Canada has created (or maybe had it for some time) a demographic destination: PrimeLiving.ca:

Part yellow pages, part cityguide it targets seniors. We’re about to see massive “verticalization” of the yellow pages industry online (and in mobile perhaps). But this demographic approach is also an interesting model for publishers.
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Sebastien Provencher also points out that YPG has a legal vertical:

July 23, 2009 at 9:06 pm |
[...] increasing diversification into different types of sites as well as verticals (see my post about Yellowpages.ca). This site will appeal to different categories of users and use [...]