Cloud storage services are rapidly becoming a familiar part of our digital life, and we will soon take it for granted that we can backup, synchronize and share our data in an effortless way. Thus even the big players such as Google and Microsoft hurry to jump on the bandwagon.
But which one these services should you use? Well, if you run your own server, consider setting up your own cloud using ownCloud. This community-driven development offers all what its commercial competitors offer and more. In particular, your data remain under your control. If all you want is to synchronize files between several locations (such as office and home), even the spartan SparkleShare (which only requires git and sshd to run) may suffice.
If you don't run your own server, you have the choice between several commercial offers which all include a basic plan which is free of charge. The most popular of these offers are, in alphabetical order, Crashplan, Dropbox, Google Drive, Microsoft's Skydrive, Spideroak, Sugarsync, Ubuntu One, and Wuala. Sorted by popularity, it's Dropbox, Dropbox, and Dropbox.
Seriously, the people I know either don't use cloud storage at all or Dropbox. But it this popularity justified?
An informed and detailed analysis of several cloud storage services has been published earlier this year by the Fraunhofer-Institut für sichere Informationstechnologie in Darmstadt. The four page management summary provides an excellent overview, but I recommend reading at least the relevant parts of the actual report.
You'll see there, for example, that Dropbox features synchronization and sharing, but no backup, and offers a server side encryption only. The free offer is limited to 2 GB, and all storage is done on Amazon's servers which are subject to US law (aka Patriot Act). Teamdrive and Wuala store on EU servers with client-side encryption and a backup option in addition to synchronization and sharing. Whereas Wuala's free offer includes 5 GB of storage, Teamdrive even provides a server component which will allow the storage of 10 GB on a server of your choice.
Whatever you chose, chose deliberately and not what the mainstream suggests.