In my procurement organization, we're required by the Code of Federal Regulations (e.g., 10 CFR 600) to use the Excluded Parties List System ("EPLS") whenever we do a procurement that is funded by the Federal Government.  EPLS includes information on vendors and individuals debarred, suspended, proposed for debarment, excluded or disqualified, or otherwise declared ineligible from receiving Federal contracts, certain subcontracts, and certain Federal assistance and benefits.  In other words, if a vendor has done something "bad" (like fraud), the Federal Government disqualifies the vendor for purposes of doing business with the Federal Government and for procurements conducted by others (like my organization) that involve Federal funds.

The cool thing about EPLS is that it's open for everyone—meaning that you can use it as a tool for your commercial procurements.  If you're considering doing business with a new vendor, EPLS serves as an important resource for doing your due diligence and research.  If a vendor shows up on the list, ask why.