If you do this, even informally, you could be setting yourself up for a lawsuit. Just because someone doesn't pay you doesn't mean they don't pay others. Credit bureaus operate under very strict guidelines and their information is collected in specific ways. Unless you are a licensed credit reporting agency you could be in violation of the law if you share payment or credit history with other businesses. In small towns word often gets around about deadbeats without your input.
Credit laws vary from state to state and country to country.
Check with your local attorney before releasing any information about anyone to unauthorized sources. Search this site by keyword.