Cloud storage ("the cloud") allows you to store your files online so that you can access them from anywhere. Your files are stored on remote servers at the cloud provider's data center. As a matter of full disclosure: I use the cloud. For me, the advantages of the cloud outweigh the disadvantages. However, I do not upload all of my files to the cloud. With it, you can access your files at any time, as long as you have an Internet connection. Your information is housed in a more secure location than the hard drive on a computer. However, you ultimately lack control over privileged documents. In the event of a legal dispute, the cloud provider determines whether to divulge your information to adverse parties.
The reason there is controversy over the cloud is that your information is housed and controlled by a third party. Typical terms and conditions for cloud providers state that the provider can divulge your information when the company deems it reasonably necessary to comply with a legal request. There is no exception for confidential information.
So, if law enforcement asks the provider for your files, the provider can release them without your consent or input. This is probably the greatest danger to criminal defense attorneys. In other legal cases, the opposing party would ask for the files in discovery before having to resort to a subpoena. Moreover, it would be extraordinarily unlikely that a subpoena would be served on the cloud provider, instead of the account holder with the provider. In the provider's defense, they would not likely divulge your information without a subpoena, since you are one of their customers.
Successful businesses face a tantamount risk as criminal defense attorneys do, if they store confidential proprietary information on the cloud. Competing businesses can theoretically hack into the cloud and access your information, although this risk is lower on the cloud than it is when you store your information on a computer hard drive or local server. But if you are not an individual target, your information is more vulnerable on the cloud, because cloud providers are a much greater target for hacking. If you are part of the cloud, your information could be hacked.
At least publicly, espionage via the Internet is growing. You regularly hear of another country accessing an American company's servers. If your information is part of the victimized company's servers, it is at risk.