Apple now limits US customers to two iPhone Duos each, and the store only says so once you try to buy a third.
Adding more than two to the cart on Apple's website or in the Apple Store app triggers a notice: "A maximum of 2 iPhone Duo can be purchased per customer. Please adjust the total quantity of iPhone Duo in your order before checking out." Pre-orders opened October 16.
Whether the cap was there from the start is unclear. Some Reddit users call the US limit new. The same thread includes customers who say they bought four Duos and others who say they were held to two. The cap could have been added after pre-orders began, or it could have been applied unevenly. The available evidence does not settle which.
The US handling differs from other markets. In China, Singapore and Hong Kong, Apple listed a two-per-customer restriction plainly. The US page says nothing until the quantity crosses the line.
There is one sign that supply may be easing. Apple appears to be moving up some delivery dates, which could mean customers who pre-ordered early get their phones sooner than first quoted.
Per-customer caps are a familiar tool for products that sell faster than they can be built. They discourage bulk buying for resale, and they spread early stock across more buyers. A cap does not, on its own, say how tight supply is. Apple has not said why it set this limit, and a quiet cap paired with earlier delivery dates is a mixed signal. The question is whether the limit stays in place if shipping estimates keep shrinking.