To give or to receive: your choice

The Freakonomics boys draw attention to an offer from a bank:

Would you rather donate $100 to a charity you believe in, or spend $50 in your favorite shop?

I suppose if people know how to buy happiness (give your money away) they'll choose the charity. But who is actually paying for this free lunch? Where's the money coming from?

Presumably the bank has figured that it is worth up to $100 to buy a new customer, and the terms of the giveaway restrict who can do it, how often, and other stuff. But you just know that the money isn't coming from the Bank President's own pocket. Would the overall banking fees be lower if there were no giveaway, either to selfish bastards or on behalf of altruistic angels?

I ask as someone who is robbed blind by his bank most days of the week. They recently charged me 2 euros to send me a letter explaining their new attitude to transparency; it was opaque.

Anyway, it would be nice if the bank made the results of its promotion available for detailed analysis.

And in other news: Kiva still has no agricultural projects I care to lend to.