The interesting bits are hidden in their legal agreement page. Section 5.1 says:
5.1 Your Files. By using the Service with Your Files, you are directing us to store Your Files on your behalf. You are solely responsible for the content of Your Files and your use of the Service to store and retrieve Your Files. You must ensure that you have all the necessary rights in Your Files that permit you to use the Service without infringing the rights of any copyright owners, violating any applicable laws or violating the terms of any license or agreement to which you are bound. You must ensure that Your Files are free from any malware, viruses, Trojan horses, spyware, worms, or other malicious or harmful code. In transferring Your Files to and from the Service, you are responsible for complying with all applicable import, re-import, export, and re-export control laws and regulations, including the Export Administration Regulations, the International Traffic in Arms Regulations, and country-specific economic sanctions programs implemented by the Office of Foreign Assets Control. Failure to comply with these requirements may result in the immediate termination of your rights under this Agreement in accordance with Section 7.1.
Okay, so that's not really all that surprising. But combined with this part, it makes me worry:
5.2 Our Right to Access Your Files. You give us the right to access, retain, use and disclose your account information and Your Files: to provide you with technical support and address technical issues; to investigate compliance with the terms of this Agreement, enforce the terms of this Agreement and protect the Service and its users from fraud or security threats; or as we determine is necessary to provide the Service or comply with applicable law.
I imagine that, after determining that you have an "unofficial" copy of a song, they'll allow you to purchase a license for it at the standard dollar per track, eh?
And if that's not bad enough, they want to charge $1 a gig for storage, per year, for anything more than 5GB (and who'd do that??? 5GB you can fit on a cheap SD card for crissakes...) and all of your files are toast if you stop paying, not to mention what the costs would be for data streaming on a phone.
I'll keep my collection on my own hard drive, thanks.