Google has been mixing things up (again) and there is a major change to the algorithm that could negatively impact your rankings. It has to do with "Doorway Pages". Many of the Plumbing & HVAC Companies I talk with serve a 25-50 mile radius covering 10-25 sub-cities & suburbs. In an effort to rank for as many of those sub-markets as possible they have created multiple "City Pages" on their website as part of their SEO Strategy. If your not carful, Google may start to treat those City Pages as "Doorway Pages" resulting in a drop in rankings.
I recorded a brief video that explain exactly what this is all about and what you need to do to ensure that your website does not get dinged in the process. Take a look: