Yes!  Absolutely right on target, Sandra.

In the first place, the post office considers packages either weighing a certain amount or that look 'strange' AND that have not been hand stamped by a postal clerk (i.e. postage stamps affixed) to be suspect ... in other words ... said package might be a bomb.  Dropping things like that into a postal collection box is actually prohibited ... there is a notice affixed to the blue collection boxes that states this.

There is no way that rice sent to the white house is going to get forwarded to the starving people in North Korea or anywhere else, for that matter.   Its unsanitary in the first place.  The idea 'sounds' good but, in this age of terrorism and crazy minds run amuck .... forget it!