Linda Buquet posted in her Local Search Forums based on a Google Maps Maker Help thread that uncovered a law firm abusing the Google Maps business/local database by setting up virtual offices through UPS boxes and/or Regus offices.
This is not new - businesses have been using these virtual offices to get approved local listings in Google Maps and other local databases for years. What Linda is saying is new, is that these cases are being outed and caught more frequently these days.
So you should be aware that if you are doing this or your SEO company is doing this for you, you should be careful. It might end up hurting your main listing.
Linda said this can be found easily by Googlers or algorithms by looking at patterns, such as the "funny looking suite #s like "Ste. C-8 #149" on their contact us page. So be careful, don't end up spamming, getting caught and drying up on leads over night.