The thing is that everything people say can be interpreted subjectively and such interpretation can be handled in a bad way. For example, let's say I post in a forum called TyrannyTalk that "I don't like that Steve guy" while Steve is a friend of the admin. The admin takes an alt army and slanders me with posts about me scamming users, presents faked proof. After that he orders the mods to ban me and poof, banned. See what I mean?

Meanwhile in BitcoinTalk people see a scammer and each user with different amounts of rep rates him appropriately. Another user dealing with him sees the ratings and makes a descision to trade with him or to cancel the deal.