DNU list
We also have built our DNU list from info on this site. Along with other things such as credit checks, reference checks, if we have been lied to, not paid, etc...
This site is a great foundation and I also agree that you will build upon it from your own experiences. Frankly, I put companies on my DNU list simply for having a consistently poor attitude. Everyone is allowed to have a bad day but when different people within the same company constantly have bad attitudes and are rude, that is a big red flag for me!
Sadly, my DNU list has grown exponentially over the past year due to bankruptcies, crappy credit, lies, and non-payment.