This is the official logo for 2008 Olympics which you can see on main page of Google from where people do all sorts of searching . Google has many logos which they display at their home page throughout the year on various occasions which include but not limited to holidays, birthdays of famous personalities , major events and yes for Olympics too .
It is not necessary that you will see the same set of logos the next year but many of those logos remain the same which includes the official Google logo .
You can view the past history of logos shown by Google at PerfNova .