The good thing about random altruism, i.e. giving stuff to people regardless of whether they need it or not, is that it doesn't encourage welfare dependency.
When you give free stuff to "those in need", you have to be extremely careful not to just wind up changing the balance of incentives in a way that just encourages them to stay "in need". Otherwise you're harming them, not helping them.
At the same time, if a few people riding the system that way is the price you have to pay to help the people who truly need it, isn't it really worth it?
I think what the grandfather post meant was that Jonathan's card is meant to be scanned from a cell phone. If things like this are restricted to people with a cell phone (or a facebook account, or an iphone app...), the system selects for beneficiaries who are already above a certain level of need.
When you give free stuff to "those in need", you have to be extremely careful not to just wind up changing the balance of incentives in a way that just encourages them to stay "in need". Otherwise you're harming them, not helping them.