Paul Schwartz quoted in The Wall Street Journal, (requires registration) July 15, 2012
Paul M. Schwartz … said the use of pen registers and trap-and-trace technology is likely up because the public is spending more time on smartphones and the Internet. … The data available to agencies is much broader than when investigators tracked phone calls to and from a single line, he said. “It’s not surprising they’re going to make use of it,” he said.