Making money with Credit cards

There’s an easy way to make a few extra bucks with a credit card that offers 0% on balance transfers.  This is what I did.
Last night I found a CitiBank MasterCard promotion that offers 0% on credit transfers.  I applied for the card letting them know that I will want to transfer $3000 from my existing card (The balance on my card isn’t nearly that much).  If the card is approved they’ll send me the card and a kit that I can take to the bank and have the money transfered to their card.  The trick is, I’ll go to the ATM and withdrawl $3000 cash from my visa beforehand and put it in a safe investing account like a no fee savings account from President’s Choice financial that gives 4% interest.  Over the year that I have the $3000 for no cost to me, I’ll be making just over $120 in interest.  Then next January before my rate gets bumped up, I’ll withdrawl the $3000 from the savings account to pay back the MasterCard, and then cut up the card.
It’ll probably require 1 hour of work (mostly waiting in line at the bank) so the payback is pretty good considering that.
How many of these could I do? As many as the banks would let me. I could borrow $3000 from each of 10 cards at 0% for a total of $30 000 if I invested that in a safe investment vehicle at 4% I’d have over $1200.  If something came up that I figured it could make 10% that would be over $3000.
Making money with other peoples money is a great thing.