To stay on topic, most people use fake facebook accounts so they don't want to be retraced while completing a RMT deal, to troll people without even caring to be recognized and at last it's easier to scam people if they don't know your real info.
I disagree with you.
People who are RMTing don't care who they are selling their stuff to.
You should always have caution when dealing with people.
In most trades no one has to go first unless it's something like WPE.
Schitter does a very good job in policing the Facebook group with not only who he allows in, but the community is also very vocal about shaming scammers and they will be promptly dealt with if proof is provided.
I can understand not wanting someone to know your info or have access to your friends list, but in reality what is someone going to do to you?
Most people already know your name in game if you're well known or have an active relationship with your guild.
You can always make a Facebook just for Ragnarok and easily confirm with friends that you are who you say you are.