Welcome back to Fraudology.
In this episode, I’m sitting down with Mark Porteous, a longtime leader in e-commerce fraud and trust who knows two-sided marketplaces from the inside out. Mark spent nine years at StockX, where he started in customer support before building the company’s fraud program from the ground up. And honestly, that is one of the best ways to learn marketplace fraud prevention because you see the customer complaints, the chargebacks, the seller issues, the account problems, and the policy gaps before anybody has officially decided they belong to a fraud team.
We get into what makes online marketplace fraud so different from traditional e-commerce. In a standard retail transaction, the merchant controls the inventory, the pricing, and fulfillment. In a two-sided marketplace, the platform may be trusting one person to sell, another person to buy, and sometimes a third person to deliver the product. Every additional participant creates another identity question, another fraud vector, and another opportunity for marketplace scams or policy abuse.
The deeper theme of this episode is market volatility fraud. Prices can change dramatically because of a sports result, a viral release, an artist announcement, a celebrity event, or a sudden shortage. When that happens, legitimate customer behavior changes, but fraudulent behavior changes too. Sellers may decide not to fulfill because they can resell the item for more. Buyers may file friendly fraud chargebacks after prices fall. Stolen cards may be used to purchase high-demand inventory. And risk models that normally work well can suddenly start treating good customers like fraudsters.
Marketplace fraud prevention cannot stay on autopilot. Fraud leaders need strong policies, clear escalation playbooks, reliable fraud intelligence, and real collaboration with vendors, data teams, customer support, marketing, product, and leadership.
What you’ll hear in this episode:
- How Mark moved from customer support into building a marketplace fraud program from the ground up.
- Why two-sided and multi-sided marketplaces create more complex identity, payment, seller, and fulfillment risks.
- How marketplace pricing volatility can trigger seller non-fulfillment, policy abuse, first-party fraud, and chargebacks.
- Why World Cup ticket pricing is a real-time example of market volatility fraud.
- How friendly fraud can increase when buyers repurchase the same item after its secondary-market price drops.
- Why fraud models and vendor strategies cannot be left on autopilot during high-demand events.
- How approval rates, false declines, fraud risk scoring, and card-not-present fraud need to be balanced during sudden demand spikes.
- Why fraud leaders need playbooks, policy enforcement, and clear escalation paths before an unexpected event happens.
- How to work with marketing, product, growth, finance, customer support, and security without becoming the team that says no to everything.
- Why strong fraud storytelling must always be supported by fraud analytics and measurable business impact.
You should listen to this episode if you:
- Work in marketplace fraud prevention, trust and safety, fraud operations, or fraud risk management.
- Manage buyer fraud, seller fraud, marketplace chargebacks, seller verification, or payment fraud prevention.
- Work for a ticketing, sneaker, collectible, resale, delivery, or multi-sided marketplace.
- Need a better approach to fraud monitoring during major events, product releases, shortages, or pricing spikes.
- Want to improve collaboration between fraud, customer support, product, growth, marketing, finance, and security teams.
