Cant invoke alt-tab window with shift depressed

http://www.youtube.com/watch?v=xpzllT9o7qc

alt-tab and ctrl-alt-tab invoke the alt-tab switcher dialog.
alt-shift-tab and ctrl-alt-shift-tab do not.

Should shift+alt+tab not also bring up the alt-tab window?

Video illustrates the issue.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: compiz 1:0.9.7.0+bzr3035-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-19.30-generic 3.2.11
Uname: Linux 3.2.0-19-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 1.94.1-0ubuntu2
Architecture: amd64
CompizPlugins: [core,composite,opengl,compiztoolbox,decor,vpswitch,snap,mousepoll,resize,place,move,wall,grid,regex,imgpng,session,gnomecompat,animation,fade,unitymtgrabhandles,workarounds,scale,expo,ezoom,unityshell]
CompositorRunning: compiz
Date: Tue Mar 20 13:52:17 2012
DistUpgraded: Fresh install
DistroCodename: precise
DistroVariant: ubuntu
DkmsStatus: virtualbox, 4.1.10, 3.2.0-19-generic, x86_64: installed
GraphicsCard:
 Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0102] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: Micro-Star International Co., Ltd. Device [1462:7680]
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha amd64 (20120102)
MachineType: MSI MS-7680
PackageArchitecture: all
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-19-generic root=UUID=3d53ca44-6af4-422d-b1b0-adf30c679a2f ro quiet splash vt.handoff=7
SourcePackage: compiz
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/23/2011
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: V10.8
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: H61M-E23 (MS-7680)
dmi.board.vendor: MSI
dmi.board.version: 2.0
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: MSI
dmi.chassis.version: 2.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrV10.8:bd05/23/2011:svnMSI:pnMS-7680:pvr2.0:rvnMSI:rnH61M-E23(MS-7680):rvr2.0:cvnMSI:ct3:cvr2.0:
dmi.product.name: MS-7680
dmi.product.version: 2.0
dmi.sys.vendor: MSI
version.compiz: compiz 1:0.9.7.0+bzr3035-0ubuntu1
version.ia32-libs: ia32-libs 20090808ubuntu35
version.libdrm2: libdrm2 2.4.30-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 8.0.1-0ubuntu5
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 8.0.1-0ubuntu5
version.xserver-xorg-core: xserver-xorg-core 2:1.11.4-0ubuntu6
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.0-0ubuntu1
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.99~git20111219.aacbd629-0ubuntu2
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.17.0-1ubuntu4
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20111201+b5534a1-1build2