Symform is an online data protection and disaster recovery service who have been around for a few years, using a rather unique storage method. They start with having no data center to store their files, but leverage the kindness of strangers.
This decentralized architecture means that you reserve a portion of your own storage infrastructure and allow Symform to control it and use it for backup storage for its other customers, as you can see in the diagram below. Data is broken into small chunks, encrypted and sent to random storage pools around the Internet. You have to contribute 150% of your own disk space towards the common pool of what your own backup requirements are.
For example, let's say you need 1 TB of online storage, so you have to find 1.5 TB of spare capacity on your local machines to contribute. You can start your first backup by sending them an external drive or move your server temporarily to a co-location site.
By using other people's storage, they can offer unlimited online backups for a flat fee. For example, up to 50 employees with two servers will cost $1800 per year. And while that figure sounds high, it compares favorably with what Nirvanix and Acronis charge for that user population. But that isn't good enough to convince some potential customers, and today they announced that storage up to 100GB in the cloud is available for free. You still have to contribute unused storage of your own to participate. You need Windows XP SP2 or higher, and .Net Framework v3.5: Linux and Mac versions are in the works.
Microsoft's Skydrive, of course, has offered 25 GB per user free, but this is more designed for individuals than for an enterprise-wide backup solution. And there are some others that offer unlimited storage, such as Trend Micro's SafeSync which has unlimited storage for $50 per PC. But most of these providers store data in a single location, although JungleDisk.com and ElephantDrive.com both use Amazon's cloud and distribute their storage pools across different Amazon regions.