I just finished an email exchange with a customer who had deleted a Curio 7 section, confirmed the alert that appeared stating that the deletion is non-undoable, and then realized he clicked the wrong button after watching over a year of notes disappear.
There are some recovery techniques we can use in Curio 7, as long as the project isn't re-opened. And there are even better recovery techniques we can use with Curio 8's more robust internal file architecture. But, in this case, it was too late to recover this particular data.
Accidents will occur, hard disks fail, bugs happen, and lightning will strike without warning. This is where a great backup strategy can save your valuable data.
The easiest, in my opinion, is Time Machine. Built into OS X since Leopard back in 2007. It backs up all changed files every hour to an external drive. I use OWC's drives and have always found them fast, quiet, and reliable. Lion added encrypted backup support and Mountain Lion added support for rotatable drives. The interface for exploring older versions of your files is intuitive and easy to use. For the cost of a cheap drive (about $100) you have peace of mind and incredibly fast local backups.
Next, a cloud backup service is highly recommended in addition to a local backup. I personally use BackBlaze. They offer unlimited backups and support monthly, 12-month, and 24-month plans. Paying $95 for two years of unlimited backups to an offsite cloud is a pretty darn good deal. Other services include CrashPlan, Carbonite, and Mozy.
You can also implement a whole-disk backup plan with either Carbon Copy Cloner or SuperDuper. Either application can create a bootable backup disk on an external drive -- basically an exact, up-to-date copy of your internal drive. So if you have a catastrophic disk crash you can simply boot off this external disk and you're instantly up and running with no need to re-install OS X and recover from either Time Machine or a backup service.
Lastly, don't forget about services such as Dropbox. Their free 2GB plan is perfect for creating periodic backups of your important files. Just Option-drag them to your Dropbox folder to quickly sync them up to their cloud.
On a related note, you may be wondering why Curio doesn't use Lion/ML's Versions feature. I'd love to but it doesn't support super large project files very well. When it needs to create the archived version it will freeze the main thread, and thus the UI, to make that backup copy. For large projects, this can result in a significant delay (measured in minutes). More details are here in the forums.
If you don't have a backup strategy then please take a few minutes to check out some of the links above.