An anonymous reader writes: At a House of Representatives hearing in July, the NSA admitted it can follow up to three hops in phone metadata. Just how far does that authority go? Researchers at Stanford crowdsourced data to find out. They discovered that Americans are often linked by pervasive phone numbers, such as voicemail systems, customer service lines, and telemarketing spam. "Under current FISA Court orders," write the authors, "the NSA may be able to analyze the phone records of a sizable proportion of the United States population with just one seed number."