Net Gain: Expanding Markets through Virtual Communities, by John Hagel III and Arthur G. Armstrong (Harvard Business School Press, 800-338-3987, 1997, $24.95), speaks to the authors' belief that, thanks to the Net, we're in the midst of a radical transformation: Buyers have wrested power from sellers. To identify, understand, and gain the loyalty of "virtual communities" of customers, you'll need to invoke new strategies.

"Many companies new to the Internet use the same formulas they depend on in the physical world," Hagel explains. "That may allow them to do things faster, but they miss real opportunities for rethinking how they do business and redefining who their customers are. They should look at going on the Internet as they would look at going into a new country--and exploit the potential unique to the new place.

"The Motley Fool Financial Forum, an investment group on America Online, has done that well. The two brothers who started the group originally wanted to do a newsletter. But they found, on AOL, that the real power lay in drawing people together to interact and share information. They created an engaging environment by allowing people to discuss all kinds of investment strategies, rather than expecting them to read a static newsletter online."