What's strange behaviour for Google

I am very interested by the internal Google Search algorithm. And some times, it could be very strange.

For example, a web site http://www.everyblock.com is not a veryfamous on google. Actually, only and approximatively 389.000 pages are indexed on Google with the search pattern: everyblock.

But the first week of May, and during one week, 28.20 millions pages were indexed with the key search: everyblock.

Strange behaviour, not ?