GPS can be used for lots of legitimate functions. However it can also be used to guide things which might have more sinister intent. Remove the GPS or spoof its position and then you have plugged one hole. WHO cares about a driver getting lost, pilots are being warned to not be over reliant upon it. READ between the lines with respect to the Olympic months, it's not something that takes a rocket scientist to work out.
From a notam a few weeks ago (Plot the Arc out and see the extents)
Q) EGTT/QWELW/IV/BO/W/000/400/5112N00158W065
B) FROM: 12/05/07 07:00C) TO: 12/05/11 20:00
E) GPS JAMMING EXER. JAMMER BASED WI 8NM RADIUS OF 5112N 00158W(SALISBURY PLAIN, WILTSHIRE). COVERAGE WI 15NM RADIUS AND ARC 355AND 050 DEG TRUE UP TO MAX RANGE 65NM AND 40000FT AMSL. AIC P046/2012REFERS. OPS CTC 01980674xxx OR 07776482xxx. 12-05-0067/AS 2.LOWER: SFC
UPPER: 40000FT AMSL
SCHEDULE: 0700-2000
Peter - in the past you have argued it could not happen and would not be allowed to happen, it has and I suspect during the Olympic period will be used at random times and possibly (due to operational neccesity) will be deployed without warning
Last week there was a trial which radiated 75nm radius from Sennybridge...
GPS spoofing was the claimed method of interception of an American UAV last year - it went into landing mode because it thought it was 2000nm from its true position and was back at its home base and thus entered autonimous recovery mode (no pilot intervention)