There's also the case in which you suspect a user of scam, but have no proof of it, who decides on such cases and where would the line be drawn?
Speaking purely from my pov, ban should be reserved for well documented scammers like 1xbit (and for exactly that reason they banner bid was refused) and not just anyone with a negative tag given by a couple of DT members when they suspect someone
might be a scammer, or something along those lines. So, I don't think it would be good to go completely wild and remove anyone suspicious (like they are often doing on some other forums) but should be reserved for those rare cases.
Cause it's a community oriented forum with no central authority. The users are allowed to give their suggestions on what could be or not be a scam, offering their evidence to that effect; Everyone else is allowed to make up their mind using the suggestions of others as pointers.
Just because we can give some suggestions doesn't mean that this forum doesn't have central authority.