Given that the results of a Google test are interpreted subjectively, its implementation is not always consistent. This reflects the nature of the test being used on a case by case basis.
The Google Web search is not the only Google search. In performing a Google test, consider searching groups (USENET newsgroups). This is a significantly different sample and represents, for the most part, conversations in English conducted by people who are not deliberately trying to sell products or reach a mass audience. Other things being equal, a "groups" search will typically return very roughly 1/5 as many hits as a "Web" search. Because group and Web searches have very different "systemic biases," hit numbers are not comparable.