Google usually changes its logo to commemorate things like birthdays of composers, artists, and national figures, and even very obscure occasions. Zombie Time pointed out that they did not have a special logo for holidays such as Memorial Day for veterans, even though I don’t know if they have in 2009. Google’s excuse is particularly laughable; read it it at Zombie Time. Today they link to “unexplained phenomenon” but do not explain why.
Hat tip: Culture Jam for Life