I am in favor of illegal sharing. First off, if you look at the artists mentioned you can clearly seen a defining line. The opposing bands aren't exactly pushing the envelope with music. I mean you have the guy representing Pink Floyd, Radiohead, and Blur. These guys are big name acts who sell out some of the world's biggest venues (or did at some point). Then you have the likes of Lilly Allen, ABBA, and Muse. Yeah ABBA and Muse are big name acts and I actually like Muse, but these guys don't strike me as "about the music." So, when music becomes "about the money" then it loses all appeal.
Secondly, they have to be making tons of money as is, you know, with tours and merch... CD sales are sort of a bonus these days. So, it becomes a thing of just more money. I think if you're a musician and you have tons of money in the bank, then just enjoy it. Why get greedy?