On their own these problems are major deterrents for current services, but the combination of monthly subscriptions and DRM for an online streaming account would be downright deadly. Once payments can't be made and a user account is frozen, no more songs. Could you imagine not being able to listen to music or switch your library to a different service because you couldn't scrape together $15? A tiered Netflix-like system might be a solution, but it's a band-aid over a bullet hole.

This brings up another point: Music is inherently different from film. While movies can be watched once, enjoyed and returned at a consistent pace, the appeal of a good album is based on repetition. This isn't to say people don't watch their favorite movies on endless loops, but how many could admit listening to their favorite album only 2 or 3 times?

It's this phenomenon that clashes with monthly flat fees. A customer can only download, listen to, and savor a limited amount of music per month. Anyone who's gone overboard on a BitTorrent binge knows there's no possible way to enjoy it all at once. Apple's (AAPL) iTunes Store works for this reason: It's pay as you go. One song or album at a time.

The trouble with existing services aside, current technology woes prevent steady progression into mobile media clouds. Digital music on a mobile device comes at the detriment of at least one of the following: Speed, quality and infinite selection. As of now, finding an open Wi-Fi connection while on the street is a crap shoot - unless you're lucky enough to live an area with citywide Wi-Fi. Satellite radio is a partial fix, but there are undeniable dead zones - such as, say, anywhere indoors. CDs and hard drives are still the only definite methods of listening to music anywhere, any time.

The iPod isn't in any danger of being usurped and won't be for a long time. MP3 enthusiasts continue to prefer the accessibility of a large hard drive to streaming files for obvious reasons. Offering users a streaming high-definition library would be a massive undertaking - but a necessary one to achieve any modicum of success.

And I haven't even mentioned RIAA lawsuits.