An idea I'd thought consigned to the grave is scrabbling at the lid of its coffin again. Powerline networking is back, for the third or fourth time. Siemens, one of the few telecommunications companies that seems to be making a success of its lot at the moment, is pushing its second-generation devices. Usual claims: hassle-free, 10 megabits a second, old problems of interference and cumbersome adaptors fixed, etc. Well, it might be true. But the only way it'll be more convenient than Wi-Fi is if it comes built in to computer power supplies as standard. Nobody wants to have to wire up an extra power point just to do the networking -- even less so if your second computer's a laptop. Siemens makes the only argument that stands up, that powerline networking is complementary not competitive to Wi-Fi, but to me it feels like the technology is a classic case of engineers spotting a nice idea and then assuming that people will buy it. I've never heard anyone say "Gee, I wish I could send data over the house wiring!" Perhaps I'm biased. I am, after all, a radio ham and do, after all, listen to shortwave rather more than is socially acceptable. And I've heard the tests done by the Radio Society of Great Britain, where signals of the same sort as used in the technology were picked up half a continent away. It interferes with the good stuff, and in the words of Microsoft: just how far do you want your private data to go today? Here's a prediction: people will still be trying to sell powerline networking in five years' time, and people will still not be buying it.