lammert - 3:25 am on Nov 1, 2011 (gmt 0)

According to their Twitter feed it affects "only 0.35%" of the sites which use the Google Maps API. But that can easily be the majority of the page views.

Hopefully it will mainly affect the shallow sites which spam the index by doing not much more than copying information from thousands or millions of companies from business registers and put them together with a Google Map on "business information sites".