Orders of magnitudes larger isn’t a lot of defense at this scale. Using Cory’s larger value of 4 cents means that $20 bucks buys you an awful lot of hashing. The estimates I’ve seen for domains are over a year old at just under 350 million, let’s round it up and call it a half billion for easy math. At that scale a modest lunch price would let you hash the 1000 most likely addresses at each domain. If you apply a small amount of thought to your search space you would get an even larger share of the domains (you can apply more to gmail.com than zark.com for example.) More importantly you can easily work the other way. I know I’ve got X number of addresses and hashing those will cost essentially nothing.
