An online backup service called "Mozy" was recently acquired by EMC. As a result, their unsustainable business model of offering "unlimited" backups for $5/month have been eliminated... Yes, let's all say it again: don't offer unlimited unless you mean it and can sustain it as more than just a teaser.
Off-site backups are good, especially when they happen automatically via the network.
But.. I think many of those services are not viable long term, and are subject to overnight failure. YMMV.
Here's the mozy story. Thouygh I think the advice on backups is bunk.
http://techcrunch.com/2011/02/03/why-does-mozy-hate-your-freedom/