Our data is key to our business - so securely protecting it and ensuring it is always available - even in the worst case scenario of the main office becoming inaccessible - is a must!
About a year ago I decided to start using Amazon S3 - http://aws.amazon.com/s3/ - to backup our data on an hourly basis securely to the Cloud. This was in addition to doing daily backups to Tape and using Acronis for backups to the network of all shares and servers
Over the course of the year it has proven to be reliable and reasonably cheap with prices recently reduced for backups to European servers ($0.150 per GB with free uploads to the end of June 2010).
In conjuction with S3 we use a very neat and useful backup client called Jungledisk - again this was extremely cheap to purchase and allows us to grab data from all locations on the network and configure various hourly, daily and weekly back up jobs that upload the data to Amazon S3 servers.
Jungledisk also allows you to create network mappings to your offsite disks and has many configuration options allowing you to keep previous versions and only back up certain types of file.
For SME's with smaller budgets than the big corporates I would highly recommend this combination as a good cloud backup solution for Enterprise data.