> You people
Are you trying to speak to the reference class that includes me? I don't drink coffee (I dislike the taste, but I wouldn't say I hate it), but I also don't have a Starbucks anywhere close enough to me that I would bother to visit it. The only thing I've done with this card is read about it.
Now, what I am is a game designer. What I'm trying to say by calling this a "social experiment," is that a system has been created here with technical restrictions, but no social restrictions—rules, but not norms. Just because, at first glance, it shares some attributes in common with systems that do have norms, such as good will funds, does not mean that that is what it is. Basically, what we're talking about here is a game.
Note that what something is and what something was designed to be are entirely different facts about that thing. The game I mentioned above, Chain World, was designed to be a semi-religious experience in the passing of a unique gameworld from one person to another. However, the system, as expressed through its rules, does not hold to that experience; instead, it is largely a game of keep-away and fundraising where whoever has the game, makes the rules, and the aspect of the playing of the "inner game" (the one on the USB stick) has fallen away almost entirely.
Similarly, although the intention behind this social experiment might have been to create a charity, the system as expressed through its rules does not make for a charity. It makes for something between gambling and leaving money laying on the street. It would be very simple, technically, to enforce socially-normative usage of the card such that it would be a charity—but that was not done, which means that a charity was not the strict intent, leaving people free to interpret the intent of the game as they please.
Also, if you think an experiment like this could possibly demonstrate "that most people are basically good," you're quite far off—the fact that the system is voluntary to join, and that consequences from inside the system do not leak outside, creates what in game design is called a Magic Circle[1]: a division between the social norms of the outer and inner "realities." When such a division is created, a new set of norms (a "social contract") is established between the players of the game, usually reflecting game-theoretically-optimal behavior considering the technical restrictions of the game world. For example, in the social contract of the players of a fighting game, the exploitation of bugs in the game to win is both allowed and encouraged.
Those who try to apply the social norms of the outer reality (such as fairness, generosity, etc.) to the reality within the magic circle, are usually considered to be wrong-headed by those who form the community of players of a game. They are called "scrubs"[2], and they call the tactics of the game's community "cheap." Basically, this is what you seem to be doing.
Now, of course, if you really see the card as a charity, and not a game, then you'll tend to be angry at the people who do see it as a game—just like people are angry at the financial industry for seeing US debt as a game instead of some moral imperative to fix, or like people are angry at pharmaceutical companies for seeing drug creation as a game instead of a moral imperative, or like people are angry at spammers for seeing selling viagra as a game instead of a moral imperative (to not do, in that case.) But none of these people will change, because the systems they're participating in create incentives for their (game-theoretically-optimal) behavior, rather than for what, outside the magic circle, would be "moral" behavior. To change the behavior, you either redesign the game to have different incentives—or you destroy the magic circle by allowing the consequences to leak, such as by making certain in-game actions have out-of-game legal consequences, and thus make the game into whatever sort of moral system it would be in regular, polite society.
[1] http://en.wikipedia.org/wiki/Magic_Circle_(synthetic_worlds)
[2] http://www.sirlin.net/ptw-book/intermediates-guide.html