I think there should be the instructions for deleting the user account (and maybe easier way in the OS to delete it?). This page (http://www.howtogeek.com/117994/how-to-disable-ubuntus-guest-session-account/) says it's possible, so why don't you do instructions for this operation?
ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: ubuntu-docs 12.10.3
ProcVersionSignature: Ubuntu 3.5.0-18.29-generic 3.5.7
Uname: Linux 3.5.0-18-generic i686
NonfreeKernelModules: nvidia
ApportVersion: 2.6.1-0ubuntu6
Architecture: i386
Date: Thu Nov 8 23:02:51 2012
InstallationDate: Installed on 2012-08-07 (93 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release i386 (20120423)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=fi_FI.UTF-8
SHELL=/bin/bash
SourcePackage: ubuntu-docs
UpgradeStatus: Upgraded to quantal on 2012-10-21 (18 days ago)
Added a section to 'shell- guest-session' to mirror linked guide.