Not sure if a similar issue has been mentioned before, but a while back I created an account and placed an order using a discount code, and jet.com promptly cancelled my order. When I asked why, they said it's due to "multiple accounts". Since this was my first order and I obviously had no clue what they were talking about, I pressed them for more information and the rep claimed that they did not have any further information beyond that.
The only possible connected account might be that of my brother who uses the same credit card billing address as me. Regardless, they suspended my account so that I can't even log in and that was that. Never looked at that site again.
Way to go jet.com... way to go.