One idea: require invitations from other, trusted by some criterion, customers.
But this would severely slow scaling.
But this would severely slow scaling.
I'm sorry sir we can't take your order because our records show that you already ripped off 6 other merchants in the last 5 years and we aren't willing to deal with you.
They track customer’s returns and calculates a “risk score.”
I once moved to USA as a student and didn't know anybody for a while. And being the introvert that I am, I had trouble making friends.
(Off topic: years later I returned "back to your (my) country”)
You can get to know someone enough to know they're not a scammer.