Based upon further information, it does indeed appear it is legitimate, so congratulations!
Regarding the way the contest was implemented, the main concern was that the zam people didn't know about the contest since it appeared on the wowhead side of things, which added to the confusion. As the contest is only open to certain countries, the address is required as a verification of residancy of some sort. There is definitly room for improvement in our contest process, and it is something that is being looked into. Generally when they fall into the category of "we get paid and some of our users get something of monitary value" they tend to get implemented without perhaps as much advanced testing as one might desire. Especially when it is marketing types doing the implementing.