ShareKit: how can you post on your facebook friend's wall?

How can you post on your facebook friend's 开发者_开发知识库wall (instead of your own) using ShareKit?

I thinks its Not Possible because of facebook security, in past facebook seems a spamming report and after that their developer portal of facebook and FQL is more powerful now rather then before. But Instead its not possible now but later it might be.. if Facebook Allow...