Comment 4 for bug 474258

In this case this encryption tool can at least check the size of mounted partition. In my case, swap was 2g, and destroyed partition was 80g. I'm sure, Ubuntu develepers will find the way to fix this bug.
"but I don't think that's any different from "mkswap" or many other system-administration tools which can easily cause catastrophic damage with a single unlucky keystroke."
They are different. When root uses mkswap - he knows he can make damage to the FS, but when I deleted a swap partition - I didn't even think that this can lead to data loss...