"Because of the legacy that arose, in our rush to conquer space, by building our first launch vehicles from expendable ballistic missiles, launch costs remain high. This in turn results in expensive satellites, because they have to be simultaneously very lightweight and extremely reliable. Many of the most critical satellites are multi-billion-dollar "battlestar galacticas" that take years to buld and launch (and, unfortunately, many of these are low-earth-orbit satellites). They are the carrier battle groups of the space-related military services. If they're taken out, it would take years and billions of dollars to replace their capability, and even if the money were an affordable luxury in wartime, the replacement time is not."
--TCS Daily January 2007