Today, however, the availability of the Universal Software Radio Peripheral (USRP), an open hardware software defined radio that sells for about $700, combined with work being done at GNU Radio project to codify the GSM waveform (also targeted for the end of this month), makes this once reasonable point of view seem quaint. Good encryption is now a must and it appears that A5 no longer qualifies.
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The practical reality is that encryption in systems like GSM always lives at some uneasy equilibrium between citizen's privacy expectations and government's desire to be able to wiretap. In a sense the question is "what is the target cost for decryption?" Or put another way, who should be able to afford to wiretap? The cost should be high enough to provide reasonable security, but governments generally don't want it to be absolute.
Of course the paranoid will know the Government is already doing this as a matter of routine on them, but for the rest of us, the full article is here.