Ubuntu's own cloud-storage service tied in with its Linux distrubiton is going to be closing down! http://blog.canonical.com/2014/04/02/shutting-down-ubuntu-one-file-services/ While on the one side this demonstrates the issue of trusting your files to a cloud service provider, at least since it synchronizes the files you don't loose your local copies, just the files stored online. That being said, if you are looking for an open source Cloud storage solution the most popular, and sure to be growing with former U1 users, is ownCloud. There is ownCloud.org for the community version and ownCloud.com for enterprises and commercial use. I don't know about you, but this is giving me incentive to set up an ownCloud server to get comfortable with it, and if I get really, really daring may even place it on a public server.