Hmm, so far on my last.fm account over 1300 tracks recorded and it still hasn't been able to calculate any musical "neighbors" for me (usual threshhold claim is around 300 tracks). Either I'm missing something or my tastes are too varied (which I don't believe for a minute).
I'm hoping there's some more-clever and smooth way to tag music for last.fm it seems like a real chore to have to duplicate info from iTunes into audioscrobbler, or vice versa. It's something of a general web problem, the technical core of "Web 2.0" is all APIs (and to a lesser degree microformats, which are on-the-fly APIs of a sort).
A couple of nights ago at MobileMonday, a fellow from ProtoHaus showed-off a demo of gearON, which apparently has already started deployment in South Korea and is designed around a "music lifestyle" (a phrase used repeatedly during the demo). gearON tries to do a little bit of everything in social media through the phone, and requires... well, everything from its users: gearOn works off of a friend list and "fuzzy" location reporting system, like dodgeball does. It accesses picture streams from all friends, like flickr does. It knows what they're playing on their MP3 devices, meaning they need to use a gearON-licensed music player rather than, say, an iPod (like last.fm does). It gets venue data and advertising revenue from venue owners like CitySearch. And it sews it up in a compact (perhaps difficult at first) UI that tries to cram as much noisy color into a small screen as is humanly possible (hey, they have a flash demo using Aki and Gray?! Go figure).
While it's not entirely clear to me, it looks from here like gearON needs to own ALL of this data within its proprietary systems. This means fighting against Web 2.0; they are competing simultaneously with Google and Apple and Yahoo while attempting to straddle the many proprietary fences of Veriizon, Cingular, Telus, et al. And they must win all or none.
If I was a smart guy with lots of time, I'd build (for PC at first) a greasemonkey or AJAX app that just did all this for you, playing nicely with all of these sevices (and preferably one that can deliver mobile-sized content too). Why should this be so hard? (Attn smart guys with lots of time: I get 10%)