Hi,
Ideally, a good editor should not add a new thing to an article without being able to say exactly where it came from.
What would be good is if we started by forcing people to specify, in broad terms, where things came from. But we didn't punish them for choosing bad sources - we would just fix it later. But at least you would know that the original writer thought it was a) common knowledge, b) personal experience, c) read it somewhere but don't remember where, d) heard it on TV, e) actually know the source, but it's dubious, f) actually know the source and it's reliable. Currently we're basically saying, if it's not f), don't bother telling us. Whereas the great majority of additions are probably in a)-d), and are being added with no source at all.
Currently we just don't know how unsourced we really are, or where the hell all those millions of edits actually came from.
Steve