Local commercial directories are controlled by a small number of information aggregators. A listing service with a relationship with these four companies can submit updates to business listings to four places and claim they have fixed more than a thousand possible ‘yellow page’ urls.
Most resources of this sort have a negligible utilization. Google has the most usage, followed by bing, and for good measure make sure your listings are accurate on Apple maps, yahoo and mapquest. That covers more than 99% of lookups.
Axciom, Factual, InfoGroup and Localeze