Building relationships with customers has been a buzz phrase in many business circles for years. Now John Hagel and Arthur Armstrong declare that's not enough. They make a strong case that business success in the very near future will depend on using the Internet to build not just relationships, but communities. The payoff, they maintain, will be phenomenal customer loyalty and high profits. But, they warn, this race will definitely go to the swift. Here's a cyberspace book that could make your business future. Not everyone agrees with Hagel and Armstrong, but with stakes so high they deserves a serious reading.