brotherhood_of_LAN - 3:49 am on May 28, 2013 (gmt 0)
Yes it'd be a big coincidence, perhaps by copying/pasting your code thinking "it works".
It could be that they're trying to jeapordise your Amazon account... but what'd they gain by that?
Does their site have any SEO-type links? It may be they have a network of sites and they're trying to throw the scent off the network by using other people's affiliate codes.