The real problem with the Youtube community (aside from lacking moderation) is that it's so big. Newgrounds is a somewhat large site, one of the top 1000 visited sites I believe I heard that somewhere. But we're relatively small in terms of people who come here everyday. If you make an ass of yourself on NG people will remember and shun you, thus removing the asses. On Youtube there's almost complete anoniminiminimity, no one will remember you so you can be a complete dick.
I like this community. On NG to submit content you need to have a specific program, but with Youtube you can just take a file and upload it without changing it. Flash is expensive so not many people are using it to make poops, windows moviemaker comes with every PC so lots of people have the ability to make, and I use the term "make" loosely, content.
Also there's the Audio Portal, somewhat more similar to Youtube. People steal things and upload them, but here they get caught. Uploading a video you saw somewhere else is difficult when you need to make it a .swf, specifically for those who don't have flash.
The system of blamming really improves the quality of content. Sure, a lot of people circumvent it, but it's much better than no filter at all. When someones Flash gets balmmed but there were a few comments form people who liked it they are inspired to try harder next time and make a better poduct. When someones Youtube video gets flamed but a few people like it they just make more of the same crap.
This is how I break down Youtubes videos:
90% Poops, screamers, video-audio mixes, videoblogs, VG gameplay footage, and other garbage.
9% Blatantly stolen things, form TV and elsewhere on the internet.
0.9% Original content, little shows and such, Jackass imitators.
0.1% Good original content.
So that works out to 1/1000 videos that are both original and worht watching.