$ sysctl vm.swapusage vm.swapusage: total = 64.00M used = 0.00M free = 64.00M (encrypted)
$ sudo defaults write /Library/Preferences/com.apple.virtualMemory UseEncryptedSwap -boolean no
$ sudo defaults write /Library/Preferences/com.apple.virtualMemory DisableEncryptedSwap -boolean yes
$ sysctl vm.swapusage vm.swapusage: total = 64.00M used = 0.00M free = 64.00M
To re-enable it run the command:
$ sudo defaults write /Library/Preferences/com.apple.virtualMemory DisableEncryptedSwap -boolean no
The advantage should be just a slightly less overhead on the page in & out process. Personally I disabled it because I am having massive page outs just running safari, and I want to test if the situation improves. Maybe disabling the secure memory bypasses some bugs. Still it is here for reference.
[crarko adds: It is just here for reference. I expect 99.9+% of people should leave encrypted VM active. Otherwise things such as your passwords can be found in plain text by searching the swap file(s).]

