I think that regardless of the origin of a work, it should be judged carefully. I've seen more than one work on this site that came from dA or whatnot that also happened to be quite excellent (at least, in my opinion) but got shot down anyway. I'm not sure if I've seen things that were crap that stayed, but I know I saw one stick around for at least a full day after I called attention to it.

The big problem with judging art is that we're all fallible, and all have different ideas of what's good and what isn't. Frankly, unless something's just so godawful hideous that you don't know how it got here, there should be some sort of grace period or something to get input from more than one or two people.

Of course, I don't know if that's possible, especially given the size of this site, but...ehh, just throwing out ideas.