Of all cases of fraud reported in 2016 at the Dutch Fraud Help Desk those related to trading on market places and webshops came 5th.
You can read the information here, in Dutch.
JanusID assists in preventing such fraud. The trading platform can ask its users to identify themselves with their verified JiD-account. The identifying data will only be available to the platform provider, never to its users. If it's clear that the identity of your counter party can be revealed, the risk of fraud diminishes sharply.