MOG is doing the name proud by bringing a wide swath of streaming music to Android and iPhone. $10 a month gives you access to over 8 million songs, and during a completely unscientific impromptu testing session, that number actually included a reasonable amount of most everything we'd want. Of course, you don't get to keep any of the 320Kbps MP3 files, merely store local copies on your phone for as long as you pony up, and even on Android (where we take task switching for granted) the merest jump to web browser stops those tracks cold. (MOG says it's working on it, at least for the iOS 4 version.)
Update: It turns out our difficulties with MOG Radio were due to a buggy preview build; downloading a fresh version of the app this morning, the Pandora-like functionality worked just fine.