• No Cloud - For starters, what do you do when you don't have access to the cloud? Streaming music assumes you can connect to the Web. If the cloud service provider experiences an outage, or your ISP is down, or you just can't seem to find an Internet connection, you will live a lonely, silent existence.

• Device Caps - Some services--notably Amazon in this case--limit the number of devices that you can use to connect to your music collection. I assume it has something to do with the licensing agreements, because Netflix also caps the number of devices I can use to stream movies. When you have the actual CD, or at least physical possession of the MP3 file, you can play it on as many devices as you want. But, if you cross the device cap threshold at Amazon you might find your entire online.

• Storage Caps - Storage space costs money and there are limits to the altruism of the cloud music service providers. They will provide you just enough gigabytes of free storage space to get you irrevocably invested in the service, then start charging you for the additional space you need to keep all your music in one place. Amazon offers 5GB for free (the 20GB plan is currently offered on a free one-year trial basis). There is a 50GB plan for $50 a year, but I have over 60GB of music which means I'd have to spend $100 a year for the 100GB plan. For $100 I can buy a 2TB external drive to store my music.

• Rules Change - This is the biggest con in my opinion. Even if the service is awesome today, rules change. The cloud music provider can bump the price, lower the storage capacity, limit the number or type of devices the music can be played on. Licensing deals could expire and content you have paid for might suddenly no longer work.

I say embrace cloud music streaming, but watch your back. You should definitely download all of your music purchases as well and maintain your own backup of the MP3 files so that you can still listen to your music even if the cloud is down, or the rules suddenly change.