Bummer indeed. It was a deal too good and Warehouse should have planned for it better. They could have made a strict limit of 1 per customer made clear in the advertisement. It would be difficult to enforce. I don't advocate printing the fingers, if you bought one already... :) But at least they could have made a little effort in order to benefit more customers. So actually I blame them. I think they should have sold them for $50 a pop, 50% off the $100 they were marked in store. That would have given them more profit and would have benefited more end customers, in my opinion.
For the record: I do buy/sell and trade Lego to recover the cost of my own hobby, but I am against emptying shelves of retailers and taking Lego away from kids. This is a fine line and could be a subject of long debate, but this is my personal opinion. None of my activities ever effected supply - demand. For the sake of full disclosure, the only time I've emptied shelves was an end of season clearance sale (75% off at Target in the States), but I believe that to be an exceptional case that can be justified.