A report from the GAO (Government Accountability Office) states that GPS systems may start failing from early next year due to a number of reasons, including lack of maintenance of satellites.
Fewer satellites, not replacing older satellites, and the rapid growth in the use of GPS devices are among the reasons listed.
GPS is being used by trucking and shipping companies to track exact location of their vessels. Emergency 911 services use GPS to track responders. Commercial airline pilots use GPS systems to get people safely to their destinations. Militaries use GPS on guided weapons to reach the correct target. Imagine if one of these things went horribly wrong!
Besides that, thousands of motorists around the world (like me) use GPS systems to find the way around town! Imagine your GPS device blacking out after getting you stranded in the middle of nowhere…
See also: Lost in the desert – with a GPS!