I created a coupon and i set it so that the number of use per customer was set to 1. However, i know it does not stop one from asking their spouse, brother, neighbour to buy with the coupon, ONCE. But today, in addition to that, one customer DID use the same coupon more than once. It is the same customer, using the same user name twice, but also using the same paypal four times (using 3 different user name).

How can this happen? Or how can it be prevented? What is it the "number of use per customer" based on? Username? or Paypal account?