Well, to play devil's advocate here, who would be the one to judge whether or not so-and-so is really ripping people off? What range products would be included in the posts that we would be allowed to make? How much information will we be allowed to reveal about the potential scammers? Would this apply only to businesses or could we also report on individuals? Would we neccessarily even have to tell the truth?
The fact is that simple rules are the easiest to enforce.
If we start making exceptions to the rules then we might as well just throw them out entirely, as i'm sure the moderators won't have time to make a judgement call on every post made by everyone who is bitching about their bad deal. In addition, posting such information is likely to reveal regional information about yourself.
"I like you, but I wouldn't want to see you working with subatomic particles."