It's part of the new 'V Stuff' from Virgin Media, probably the extras they were talking about.
You can backup/store your files/photos but how much space depends on what package you have, M/L have 5gb, XL Package has 10gb and XXL has Unlimited (Fair Usage applies obviously) - Works on Windows PC's only, not Mac or Linux.
http://www.virginmedia.com/myvirginmedia/vstuff/