Daring Fireball makes an interesting point about Ping. Yes, it's cr*p on your PC, but better on a mobile:
Ping on the iPhone feels like a decent native client to a social network. Ping on the desktop (Mac/Windows) feels like an afterthought to iTunes — one little source list item halfway down the list, with content that doesn’t seem designed at all. Not that it’s poorly designed, but un-designed. It takes the shape of default iTunes Store content.
There is an interesting thought here - simple, low grade socnets will work beter on mobile, more subtle ones that need more subtle interaction with others also need more UI with the machine.
Sort of a Shannon's Law for Social Nets, ie the bandwidth of the channel determines the social information it can carry.