i think you will come up with the same problems others have, they just change their user names

a wall of shame might be a good idea if you have had troubles with one particular individual or company, a "one time post about the problems and the end reslut" type thing for each individual issue per customer might work so, for example:

"i bought some stuff from this bloke joe smith of joe smith car parts located in skanktown englandshire, it was crap, he gave me shit, avoid"

followed by:

"i got some hevies around, he shat his pants, i got my money back, but i still think he's a cunt"

you'd have to balance it out with a "big up" room to go along side the "diss this place" room so you get positives as well as negatives

it couldn't work any other way, and, of course, if it turns out that the poster is telling porkie pies, the person being falsly accused should have their name unshamed