Anyone know why they switched the shortcut for "view shortcuts" from the Gmail/ Google Reader "?" button (shift+/) to "Ctrl+Alt+/"? Seems strange to me, as "?"

Anyone know why they switched the shortcut for "view shortcuts" from the Gmail/ Google Reader "?" button (shift+/) to "Ctrl+Alt+/"? Seems strange to me, as "?" makes intuitive sense and adding a modifier key (like ctrl) would be sufficient to distinguish between shortcuts in Gmail and those in the OS.