This one was VERY tricky, since Google Chrome doesn't use any of the conventional means to pin an icon to the taskbar and the desktop. However, there is a specific area of the registry that, if deleted, prevents this behavior. The contents of HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components{8A69D345-D564-463c-AFF1-A69D9E530F96} in .reg file format are:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{8A69D345-D564-463c-AFF1-A69D9E530F96}]
@="Google Chrome"
"StubPath"="\"C:\\Program Files\\Google\\Chrome\\Application\\24.0.1312.52\\Installer\\setup.exe\" --configure-user-settings --verbose-logging --system-level --multi-install --chrome"
"Localized Name"="Google Chrome"
"IsInstalled"=dword:00000001
"Version"="24,0,0,0"
IF YOU DELETE THIS ENTIRE SECTION:
[-HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{8A69D345-D564-463c-AFF1-A69D9E530F96}]
...then Chrome stops pinning itself to everything with every new user. In testing, the only ill effect is that it seems you will need to add a shortcut to Chrome to the Start Menu (I guess the setup.exe program adds the shortcut as well).
Hope this helps...