When I see a review posted on '2009-05-02' I never know if it's February of May.
(From My Month Long Horror/Halloween Marathon: 2008 on October 12th, 2008)
Well... think about it. I was never taught that different format. Even though it is obvious that the first number is the year... but especially at the beginning of the month I have no way to know if it is going Year Month Day or Year Day Month. Since I was never taught such a thing I have no idea what other people will write... so can't be sure.