@arkanoid: The rainbow tables used for decryption are currently distributed via P2P and yes, it requires petabytes to store them, but this is done via cheap usb sticks and cascading usb-hubs...

It is more likely to encounter an active attack than a passive one, for these reasons. It's just simpler to do. And someone would still be able to catch SMS through that, because they're the network.

PS: A5/3 is already on it's way to be broken or being exploited because it shares the same keys as an A5/1 connection. They called that weakest-link approach or something like that.