From the Volokh Conspiracy:

“Asking millions of Americans to sign a birthday card for the President suggests a tone-deafness about the cult of personality. If we lived in a dictatorship, getting millions of subjects to celebrate the Dear Leader’s birthday would be routine, but in a free republic this appeal to get millions of citizens to celebrate a current president’s birthday strikes a discordant note to my ear. No, I am not saying we are in a dictatorship; I am saying that because we are not, we should not be emulating the trappings characteristic of that fundamentally different sort of regime. Nor do I think this is particularly ominous.” 

No, but revealing and down right creepy.

Update: a different reaction here.