You Can Take It with You

As recently as two years ago, few people outside of geekdom had even heard of voice over Internet Protocol (VoIP), an inexpensive way of making phone calls via the Internet. The technology used to suffer from tedious software and poor quality. But today, VoIP is so widespread — an estimated 15 million consumers worldwide use it, according to London research firm Ovum — that you may well have made a VoIP call without knowing it. Now, unable to beat VoIP, everyone from big telecom firms to mobile service providers is rushing to join it.

This spring in Britain,...