I cant say anthing for the US version of WoW, but each time I open my European WoW theres a Blizzard message saying something like "we know you all are eager to join the beta testing of WotLK but there is no such thing going on right now and Blizzard has not send out any mails"

And there is no news about the Alpha test for friends and family of Blizzard is over.

So my money is on that this is clearly a scam.