In the beginning, the Web was social. When Sir Tim Berners-Lee created the World Wide Web at CERN in Geneva, Switzerland, in the early 1990s, his motivation was to improve communications, mainly among researchers. On his website, Sir Tim writes, “I found it frustrating that in those days, there was different information on different computers, but you had to log on to different computers to get at it. … Finding out how things worked was really difficult. Often it was just easier to go and ask people when they were having coffee.” As the Web became popular with people other than scientists, it was often used for “personal Web pages”–a very social use of the Internet. But something peculiar happened when the Web was commercialized. Because the people who built the first Web businesses were mainly the venture capitalists, consultants, and entrepreneurs of Silicon Valley, the first dot-coms were largely concerned with using the Web to improve the efficiency of existing markets for products and services like books, groceries, stocks, and software. Alas, afloat in a sea of venture capital and the cash from premature public offerings, too many such companies were themselves highly inefficient: their strategies were, in essence, to get big quickly by giving goods away for a fraction of their value. After the Internet bubble burst in 2000, all but the most profitable of these experimental ventures vanished. Since then, Web 2.0, with its emphasis on collaboration and communication, has become overwhelmingly social–a nice return to the Web’s foundations. An entire generation of young people has come of age using the Internet as its dominant medium for socializing. But although tens of millions around the world use social networks like Facebook and MySpace, the future of the Web is obscure. Many people, this editor included, fret that the second Web reminds them of the first, just before the bursting of the bubble. In this issue of Technology Review, we examine how social networks might make money; why the ownership of personal data on Web 2.0 sites is so fraught an issue; and how the Internet will support the swelling tide of rich media that people are sharing. We also identify 10 Web 2.0 startups that we think are particularly promising, and visit the offices of one of our favorite new ventures, the microblogging service Twitter. Finally, we ask some of the founders of the Web and its contemporary innovators to tell us: “What will be the future of the Web?”