More importantly it is not up to 3rd parties to dictate to the rest of the forum what their acceptable level of risk is.
I mean, I agree with you here, but that isn't what Default Trust does. If we were banning these users and deleting their threads, then you would have a completely valid point, but I disagree that simply putting the words "Warning: Trade with extreme caution" under someone's avatar amounts to dictating to other users.