A few days ago, Jean Veronis informed me of a blog posting of his named Web: Googlean logic [en], which describes in great details the issues brought up in a thread at Search Engine Watch Forums named Impossible Counts. Basic idea is that the Google Count provided in the form of "Results 1 - 10 of about 5,000,000 for keyword phrase. (0.10 seconds)", the 5,000,000 or whatever number is there, is simply impossible. I strongly recommend reading the entry and discussing this at the thread.