This article is one in a series of 10 stories we're running this week covering today's most significant emerging technologies. It's part of our annual "10 Emerging Technologies" report, which appears in the March/April print issue of Technology Review.

Ted Stevens, the 83-year-old senior senator from Alaska, was widely ridiculed last year for a speech in which he described the Internet as "a series of tubes." Yet clumsy as his metaphor may have been, Stevens was struggling to make a reasonable point: the tubes can get clogged. And that may happen sooner than expected, thanks to the exploding popularity of digital video.