I discovered a Memopal (www.memopal.com) “cutting edge solution for online
backup”

They merged online backup, online storage and file sharing services into one product.

If you try this service you will notice that (contrary to most competitors):
– You can access your files in (true) real time with a web browser
– They really offer 250 GB (some competitors offer a fake unlimited web
space, they say “fair use”)
– You can share a file or many files with the 1-click-share functionality
– Some of your files will be uploaded very very fast (turboupload)
– The service and website are in 10 different languages

I’ve also found two useful guide to online backup on Wikipedia:
http://en.wikipedia.org/wiki/Online_backup