If early last September you'd parked outside Lehman Brothers' Manhattan headquarters with a cell-phone scanner and listened only to some of the "chatter" coming out of Lehman's front office, you almost certainly would have realized that Lehman was going under.
(Of course, listening to cell-phone conversations with a scanner in this country is flatly illegal. And you need a sophisticated decrypting device to listen to most cell-phone calls.) Chatter is one of those floating espionage terms that can mean anything from secretly intercepted telephone calls and e-mails to the volume of communications traffic at a particular time over a particular line. America's 16 intelligence agencies by and large consider chatter the most reliable intelligence there is. But they also need to constantly remind themselves that it is a blunt tool, often as confusing as it is illuminating.