Tbh its pretty self explanitory... "new"comer meaning they are new which means they arent accustomed to the site. therefore making them vulnerable to being a scammed victim.
They won't get scammed often. You can't immediately assume because you're using a trusted MiddleMan the trade will be safe. Yes, it is much safer, but there has been too many instances in the past of trusted members and even staff using their ranks to scam. Be smart all the time.