it's the complete record of all bitcoin transactions that "can't just be deleted from existence."
even if the net goes down the blockchain will still be saved on everyone's computer when the net comes back on. if it does not come back on then we have much bigger problems to deal with than bitcoins and credit card transactions.
Official Daily Paul BTC address: 16oZXSGAcDrSbZeBnSu84w5UWwbLtZsBms
My Bitcoin: 17khsA7MvBJAGAPkhrFJdQZPYKgxAeXkBY