Thankfully, nothing has happened to me as of yet. Since very few of my projects are built on-calc, I haven't had much of a problem with calc corruption. Back in my "earlier" calc programming days, in which I did build stuff on-calc, I've been blessed with a calc to computer link cable for the entire experience, so I've been backing up. Most of what I did "lose" was at most an hour or two worth of work.
In this distant "future", I personally don't miss anything that I've lost in this way. As for my ASM projects, I keep multiple backups where I deem useful. Multiple backups of my entire development environment has been made to several flashdrives and a few computers (some of them date back so long that I'll look over them just for nostalgia purposes).
Currently, CaDan is protected in part by a not-so-recent email to myself with relation to the project. A copy was made to my 16GB flashdrive and an "active" copy is always in my laptop, sitting both in the dev folder and in the SD card. The idea for using the SD card came from a friend in the math lab, who reminded me that laptop harddrives are notoriously flaky. This one hasn't caused problems yet, but I still keep backups of full source on my SD card.
Backups include WinRAR'd "past" versions of the program, with a current version sitting as-is.
Celtic III is, in part, backed up by multiple flashdrives, and the postings on UTI. Retracing my steps through the various versions shouldn't be that hard, in the event the most recent one is lost.
In short, even though you'll hopefully never use them, ensure that your backups have backups in all sorts of medium, including USB flashdrives, SD cards, multiple computer HDD's, email accounts, and if you want open-source, full source posted to the forum(s) of your choice. Especially the forums, since you can pretty much go anywhere and work on your program, with or without your dev environment.
If it's an on-calc thing, ensure that you regularly "group" changes (which saved me many times). If you have a cable, transfer those groups out and onto a computer. Never allow anyone to touch your calculator. If someone wanted to borrow your calculator, the following excuse has usually worked for me : "Can't let you borrow this. It's in development." If that doesn't work a stern "No." works after that.