I suspect a world without copyright would look a lot more like the sistine chapel than it's defenders want to admit.
PS: I would accept Movies as a good counter argument except even 10 years of protection is overkill in most cases due to both the diminishing income streams and time value of money.
The internet has certainly made it easier to get content out there. But it has also made it very evident how rare good talent actually is. The good ones deserve to be able to be rewarded for their work so they can continue to produce more, and unless someone comes up with a better system, copyright is what we have.
Minimally biased raiting systems seem like an effective way to seperate the dreck. Yet, paid content has huge incentives to game the system, but with unpaid content that's far less of an issue.
For example, if a photographer takes a picture of something and posts it to their online website, without copyright anyone could just up and steal it and claim it as their own, and there'd be nothing the artist could do about it.
Same thing for writers. And video directors. And musicians. Etc.
Yes, it's misused and could use a lot of improvements; however, it's here for a good reason.
Bottom Line: You can improve something without completely getting rid of it. Creative Commons (CC) is a great example of this; it allows for open sharing yet maintains attribution. This protects the artists whilst dismantling any motivation for publishers/distributors/other_companies to be copyright sharks about it.