I don't even really mind that it's not so much a social networking tool as it is an excuse for people to buy more shit from the iTunes Music Store; Apple has mouths to feed and lobbyists to pay off just like e'rrbody else. But the fact that it's ONLY an excuse to get people to go to the iTunes Music Store -- that is, that its functionality outside of it is limited to agreeing or disagreeing with what Katy Perry or Rick Rubin think is a good single -- makes it pretty worthless, and not much of an improvement on just going to the Music Store and putting in a rating like you could before.
It's pretty counter-intuitive from the jump-off; the fact that none of the materials tell you how you can actually do the one interesting thing (rate and review albums), and that you have to figure out by trial and error that you do it by going to the iTunes Music Store and posting from a song or album's page, makes it feel all the more like you're just participating in a cheap marketing ploy. Same goes for the "we gave these celebrities a big check" feel of the extremely limited number of people you can choose to 'follow' a la Twitter, and the fact that you can only review music that is for sale via the iTunes Music Store. It seems to completely lack that 'whoa, cool' quality that Apple is so good at, that ability to make you think you're seeing something you've never seen before. While Google Wave seemed incomprehensible -- no one was ever able to figure out exactly what you were supposed to do with the thing -- Ping seems all too comprehensible, all too obvious, all to clearly nothing more than a fancied-up way of getting you in front of a "buy me now!" button.
I can see some potential for it, if people start using it for reasons other than Apple paid them to do so. In fact, I could see a great way for it to be a cool musical networking tool: if it let you go into your existing iTunes music library, write reviews there, and have those reviews uploaded to your Ping page, that would be real social networking. As it stands now, though, Ping sounds a lot like one of those poorly-thought-out, overly hyped projects we usually get from Microsoft, right down to the suspiciously familiar name.