I had thought that the only down-side of Last.fm (aside from its tendency to take up far too much of my time) was its incredible bugginess; it's the most bug-ridden and prone to collapse of any site that I've been involved with. It now turns out to have the worst moderators I've come across. I'd thought, naïvely, that a site based on shared love of music would engender a better, not a worse spirit of community than a general site (such as, say, Wikipedia). In fact my interactions with other users have borne that out, so it's especially saddening that it doesn't extend to the people whom one might have expected to set the tone here.
[The main and worst culprit was Jester-NL; I've since seen his work elsewhere on the site, generally abrupt to the point of rudeness, absolutely sure of his own rightness even (especially?) when he's wrong, and misusing (to my eyes) his moderator's powers (see, e.g., Saban Bajramovic, where he's declared the spelling to be incorrect, pointed to the also incorrect Šaban Bajramovic (it should be Šaban Bajramović), and locked the artist bio with his mistake in place so that no-one can correct him. He did the same thing at Kudsi Erguner, which he wrongly insisted should be Kudsi Ergüner; in that case, he also replaced the photos with a red "keep stats clean" image. That mess has been cleared up now, fortunately.]
And he's done the same thing at Aynur, insisting incorrectly that she be tagged Aynur Doğan. See the relevant forum discussion.
(See also http://www.last.fm/group/Group+Leaders+Support+Group/forum/69206/_/328076 .)