Now on one level this is more re-assuring than having it all on your own PC, after all Google's servers are less likely to fail than my laptop, right? Well probably but if they do then would they have a backup? How long would it take to get it back?
One answer is to ensure you have it all stored at home as well and this might work fine for photos etc but for real cloud based services (Facebook, Twitter, Blogger etc) this isn't so easy. And also making sure you remember to keep those photos you uploaded from Flickr on holiday from your laptop on a desktop at home might be a problem.
Backupify is one possible answer to this. It provides a currently free (if you sign up now) automated backup service which stores your content on Amazon's S3 storage service with a web front end. Sign up at http://www.backupify.com, run through the setup which in most cases uses the normal API authentication to services that means Backupify doens't need to store your username and password.
I've used the service since just after Christmas and it seems to work fine. It did take a few days to actually get all my content but now I can login and actually browse and see the content (which is reassuring) and every day it emails me a report on what it has backed up - so tonight I should get one saying it has backed this article up!
One slight word of caution, there seem to have been some issues with Gmail backup so I haven't used that yet. Not sure how long this will stay free for but it might be worth paying for? But it is currently free so worth a look.