An article in the Wall Street Journal refers to the financial firms that sold credit default swaps on homebuilder Hovnanian to the Blackstone Group as having sold Blackstone "insurance." In what sense are credit default swaps a type of insurance?

An investor $($buyer$)$ pays a premium to the seller of a credit default swap $($CDS$)$ to for an asset such as a bond. The investor would only receive money back from the seller if the asset the CDS covers