Has anyone considered that Discover (just like any other credit card company) probably has a swipe fee / purchase algorithm which differentiates based on each product being purchased? For example, Discover may get a flat 1%, 1.5%, or 2% "swipe" fee on the purchase of a $200 DVD player, but when purchasing Gift Cards I am sure the contract is a little more complex. I would bet that Discover doesn't get a flat 2% fee of $10.10 when someone purchases a One Vanilla card and loads $500 dollars on it - they probably get a small fee of less than $1. If we can assume that this is true, it would then be relatively easy for Discover to figure out what was included in a total purchase based on the swipe fee they get, even though they can't distinguish exact individual items.