The GM CFO post traditionally has been a job for auto industry insiders, if not always GM lifers. Ex-CEO Fritz Henderson, for instance, was CFO. Another ex-GM CFO, John Devine, had been CFO at Ford (F).
Assuming Liddell brings some lieutenants with him, that could have a ripple effect, since it probably frustrates the career plans of additional GM career soldiers. The CFO job has also been a path to the CEO job, so Liddell becomes a candidate for that post, too.
Officially, Liddell doesn't leave Microsoft until Dec. 31.
Second, Liddell's appointment is a sign of growing cross-pollination between the U.S. auto industry and the computer industry in general, and Microsoft in particular.
Microsoft is already an important partner with Ford, since Microsoft co-developed Ford's popular Sync system. Sync allows a car's occupants to use voice-control, to control portable devices like cell phones and MP3 players, and to listen to them over the car's speakers.
Microsoft also helped develop a similar system, called "Blue & Me," for Fiat. The Fiat takeover of Chrysler probably means Chrysler products get access to the Fiat system.
In comparison with Ford and Chrysler, GM so far has taken a different approach to its in-car communication system, OnStar. Instead of using the owner's portable cell phone, OnStar uses what amounts to an onboard cell phone, hard-wired into the car.
It's still a stretch, but all these parallel developments make a jump from the computer industry to the auto industry less of a leap than it appears.