More of a "business hack" than a technology hack. He utilized tech to manipulate an existing market to his benefit (getting top designers to participate) and then used it to help promote his own product.
hacking is getting access to something you shouldn't have, which is not what he's done. It's definitely clever, don't get me wrong, but the use of word 'hack' here was solely for PR
Urgh. The value of the word hacking has been undergoing so much inflation in the last couple of years that you're now considered a master hacker if you can write a simple web spider.