I remember reading a story posted here back in February/March that was about a Swiss company [the name slips me] that sold satphones that were supposedly anonymous. They were a favorite of the terrorists. The gist of the story was that the spooks somehow got a way to make some id's and that was a major step in catching KSM. I do recall the "source" of the story saying that AQ caught on to what was happening, and radically curtailed use of the phones, so revealing the "secret" was considered no problem.
Still, since we know their favorite make and model, it wouldn't be difficult to track down the retailer they're buying from. Bobby trap the phones.
--Boot Hill