It doesn't, but you can cut-n-paste the text into your own e-mail system (yahoo, hotmail, etc) and hit send! :)
Oh, yeah? And what if the readers at the White House are like FReepers, who only read the first couple words of any story before making up their mind about it? If they get several Kerry petititions and then read the first line of FReeper modification, they will think it's a Kerry one and toss it anyway.