Teenagers have long been the vanguard of popular culture, which explains why so many adults are only now taking a close look at the social-network sites that young folks have been flocking to in recent years. The MySpace personal Web page service boasts more than 90 million accounts, primarily registered by teens. Similarly, college students account for most of the 7.5 million users of Facebook, though the service is expanding to include other schools, companies, and geographical regions.

Social networks are far from the sole province of youngsters, however. Services such as LinkedIn and Ryze have a clear business focus. But whether for work, fun, or a combination of the two, it's vital that you maintain strict control over your various online personae.

Turning traditionally private pursuits into public events often comes back to haunt online revelers. Just as companies create a corporate image that conveys their core purpose and virtues, individuals project an online image through social networking sites, blogs, e-mail, photo and video sharing, and other online activities. Your image can have an immediate impact on how friends, family, strangers, and prospective employers view you. You want to express your individuality, but you also want to get hired. By following the proper steps, you accomplish both.