I don't know, but this may be a cheaper way to get Voodoo tickets. I doubt a CD pre-order and a t-shirt are the same price as Voodoo tickets.....unless they only let you in to see Deadmau5....but even then, who's checking?
Besides, you also get a Deadmau5 CD and T-shirt! Win win win. Signing up to be a HT+1 member is free and you can choose to ignore the emails about irrelevant merchandise.