Charity vending machine

Concept: Most machines offer a product in return
for inserting money. This one offers nothing except
a feeling of contribution as you have donated that
money to one of the nominated charities on the
"vending" machine. A variation of this machine is
that you buy an item and have the option of donating
your change to a charity of your choice from the options
available.

I think the main strength of this idea is that people
always use vending machines because they are
available everywhere. Also they can easily donate
money to charity while they are buying some drinks
or snacks. So as I said before vending machines can
be located everywhere. That is another strength.
They can be located in schools, universities, offices etc.
I can't see any serious weaknesses. Maybe only that
not everyone would like to donate money for charity.