(Edited lightly to increase its generality. Incidentally, this little chunk of text is closely related to the rationale behind Starfic.)
...Writing is easy--all you need is an opinion and a keyboard, and there's no shortage of either. What's hard is reading and thinking about what someone else has said. Writing something crappy still makes the writer feel good; reading something crappy makes the reader feel he's wasted precious time.
I see this everywhere. I see this on fanfiction sites where Mary Sues written by pre-teens who can't even grasp the concept of a capital letter are given the same level of respect as masterpieces written by people whose storytelling ability rivals Stephen King, J.K. Rowling and Tom Clancy. I see this in the media, where crackpot theories are given as much weight as carefully thought out and researched ones.
In a quality-controlled environment like professional novel writing, the writer deserves a great deal of respect--she has jumped many hurdles and proven herself superior to the competition. But in an anything-goes environment like a message board, the writer is nothing. The writer will be happy whether his writing is awesome or abysmal. The reader is a saint, risking her limited free time on uneven writing.
In this environment, we need to give respect to the reader, not the writer. And the way to respect the reader is to limit the number of posts she has to read, and organize them so that she can more easily find the ones she's interested in. This means she's more likely to read things she won't consider a waste of her time.
And oh, by the way, the discussions will be more interesting for the writers too, as they'll be able to build off of each others' opinions. A win-win situation--how about that?