You have a lot of good points, in fact I'm very curious about the legal ramifications of backing-up someone else's work without permission. From a legal standpoint, I think the issue seems like it could fall into a gray area, depending on the specific case, but what about the potential value to society?
If information is available that has a positive social impact, shouldn't it be preserved? We preserve things from days gone by, works of art, books, poems, etc, for the betterment of society and to give us a better understanding of ourselves. Why does this no longer apply to today's world? I'm truly curious why this has changed in modern times (I know the direct reason is copyrights) and I wonder if it's for good or bad.