Based on this thread. The argument in a nutshell is that with the community at large having gone through the first round items, we're all judges now, and a single thread would be so chaotic as to be unusable.
I am personally of the opinion that message board psychology means that this year, everyone will end up making separate threads for their items anyway, just to be able to find the responses. It's merely a question of whether they do it in RPG Superstar/General Discussion, or RPG Superstar/Critique My Item (or whatever you want to call it).