Good IT practice tells us to backup, backup, and backup. As with our files, the same with our blogs. You never really know when something can happen to your server, as recently befell a friend of mine whose web host, Netfirms, unceremoniously deleted 90% of his data. Or another friend whose Blogspot blog Google decided acted as a transmitter for malware and promptly took it offline now and forever. Scary stories, yes, but really, such things happen.
Good thing that most modern blogging tools now have Export options. I make it a point to use Export to back up my blogs weekly. It's not that difficult, too. For example, on Blogger, the Export link is under Settings.
Now if only it weren't so close to the Delete Blog link.
On the other hand, it's far from an ideal solution. Export only saves the posts in the blog, not the images or the template. So if Picasa were to go, well, that's a lot of lost pictures there. The only solution that comes to mind is to wget the entire blog, but restoring it becomes a whole other problem. Nothing to do but keep my fingers crossed.
On the other hand, Export is better than nothing. If Google decides to muck around with my blog, that's roughly 12.3MB of text posts that will be lost. Shudder! Five years down the drain!