One reason to state the name of the individual or company, when you think you've been duped, is to warn others. If someone just says he had a terrible experience with something sold or bought on the FAOL site without being specific, how can it not reflect and effect all of us?
A negative comment about a transaction gone bad with vagarities, non-specifics and generalities about the identification of the offending party leaves us all guessing. Maybe the next time any of us thinks of buying something, we'll wonder if the person listing the item can be trusted? Maybe he's the person who scr*wed John Doe? Also, if you're about to sell something maybe potential buyers will think twice about buying.
I say, 'air it out'. If someone thinks they've been scr*wed and says it in the right way, it's just an opinion. The last time I looked, opinions were not slander.