What a day did I pick to check out Newgrounds again...
While I understand the legal necessity for this announcement, I do admit I am saddened by it. It's not just parodies, but good, transformative fan works that are thrown under the bus and will have no large scale venues for viewers. I definitely am of the belief that original work, no matter how terrible it is, is of more societal value than even the best fanart, but unsolicited and an unauthorized fan works have their place as well, and it need not necessarily be under a rock.
This, I suppose is the double-edged sword of Newgrounds' growth. With great audience comes great responsibility. It's just sad because unlike some other popular sites, there is a relatively higher bar for submitting a material. It's a lot harder to make even a short sprite Flash movie to a music video than it is to set up, record, and trim a clip of oneself unpacking a box, but according to the eyes of the law, the former is copyright infringement and lawsuit-bait, and the latter is okay,
Besides, if I didn't know better, I'd suspect the original post was reverse psychology at work.