I recently just let the trial period on the mobile version (ios jb) lapse without buying a subscription. While I love the idea, and I love the app itself, the music quality simply isn't there. Now, I know the bandwidth limitations that come with 3g, and I know the quality is as high as you can get it, but it's just not good enough. Which makes me think that you guys might be peaking too soon. I can't see you making money off free web users with your (thankfully) unobtrusive ads, I don't see any real reason to pay to use the web version, and I don't see mobile infrastructure being fast enough to support you there, where it seems your real prime usage case is.
Even if Google and Apple weren't booting you off their platform, how would you survive long enough that you could deliver the same quality music through my phone that I already have on my phone?
For some songs. Other song have given me a "not available on mobile" (or something to that effect) message. But those songs are not available at any quality.