And just to be clear, in the US that includes AT&T and T-Mobile as carriers that use GSM. So all you iPhone users out there, take note. Verizon and Sprint use CDMA which isn't affected by this. In Europe, pretty much every phone for every carrier is GSM by government mandate.
It's also important to note that this is only the first time the RESULTS of GSM encryption cracking being made public. It's been done before, but the results were always kept secret.
GSM. Cell phones cracked.