There are two obvious downfalls to cloud storage: cost and availability. When you buy a hard drive it is a finite, one-time investment. But, cloud storage--beyond the 5GB or 25GB you might get for free with some services--requires an ongoing monthly subscription cost.
The cost per month is less than what a drive would cost, so initially the cloud service seems significantly cheaper. Eventually, though, those monthly fees will add up to more than what the drive would have cost you, and you will still have to continue paying them each month.
Availability is an issue because you are dependent on a stable, high-speed connection to the Internet in order to access your data. If the cloud storage provider suffers an outage of some sort you also won’t be able to get your data. Some services, like Box, provide a local folder that stores data offline and syncs with the cloud when connected, so you at least have the means to ensure that the crucial data you are working on right now will be available even if the cloud is not.
Another concern is security. Along with the benefit of being able to share your data with virtually anyone comes the drawback that virtually any unauthorized user might also potentially gain access to your data. You need to make sure your data is encrypted--both in transit, and at rest in the cloud--to prevent any exposure or compromise.
Choosing a Cloud Storage Service
I don’t believe there is a “best” cloud storage provider. Personally, I use Box, but there are unique pros and cons to each, and the one that works best for you may be dictated by the mobile devices and platforms you use, the types of data you need to store, or the services used by people you need to share and collaborate with.
For example, if you work in a Windows-centric world, and you use a Windows Phone smartphone, it makes sense to look more closely at what you can do with Microsoft’s SkyDrive. If you rely on Google products and services, and you use an Android smartphone, the seamless integration makes it appealing to use the online storage offered with Google Docs.
Both of these solutions are limited, though. They offer a generous amount of storage space for free, and provide a means to share files with others, but if you are trying to extend your available storage space to the cloud, you need a more comprehensive service that offers capacity more equivalent to the hard drive you would buy if you weren’t using the cloud.
The options are many, and the list is growing. Take a look at Box, DropBox, SugarSync, and others. To choose the one that works best for you, make sure you consider whether the cloud services has a client or apps available for the operating systems and mobile devices you rely on, and that the businesses or individuals you work with will be able to access files if you share them out.