Subscribers to paid accounts on the cloud storage service can now use it to sync files between computers, in addition to the sharing and collaboration features already offered.Wuala, owned by LaCie (and pronounced "Wa-la"), is in that growing space that's not quite online backup, not quite straight cloud storage, but a kind of hybrid. The service encrypts files on your computer and distributes them across multiple servers for security. With a Pro plan, you can schedule backups, and Wuala maintains a version history for each file, enabling you to retrieve older copies if necessary. You can access the files from any computer whether it has Wuala installed or not, and you can share files by sending links. You can also set up groups give several people access to the same set of files.

The service has now added Sync to the suite of features in its Pro packages. You designate a folder on each of your computers as the Wuala Sync folder, and from then on, any file you add to one of the folders is automatically propagated to all the other ones.

The basic service is free for one GB of storage, but that doesn't come with backup, sync, or versioning -- it's straight uploading and sharing. Pro packages start at $29/year for up to 10 GB of storage up to $129/year for 100 GB of storage. (More storage is available with custom pricing.) Wuala also offers an intriguing alternative to paying for a Pro plan: you can "trade" unused disk space on any of your computers for extra space in the cloud. Trading brings Pro status along with it.