PR agencies and other organizations looking to communicate with the baby boom generation, those 78 million Americans born between 1946 and 1964, know that this group is a skeptical lot.

They lived through the significant social changes of the 1960s and '70s, after all, and tend to be more likely to follow the opinions of their peers than figures of authority. And so, in reaching out to boomers online, it's best to focus on social-networking Web sites, from general topic sites ...