I've downloaded Mavericks from the App Store, repartitioned a 32GB USB key, and followed the instructions. Specifically, I ran:
sudo /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ Mavericks.app
Here's the output. As you can see, it fails with an error:
Ready to start. To continue we need to erase the disk at /Volumes/Untitled. If you wish to continue type (Y) then press return: Y Erasing Disk: 0%... 10%... 20%...100%... Copying installer files to disk... Copy complete. Making disk bootable... Couldn't mount dmg /Volumes/Install OS X Mavericks/Install OS X Mavericks.app/Contents/SharedSupport/InstallESD.dmg (error code 112)Mount of outer dmg failed. Done.