Nostalgia is a very powerful emotion. We often find comfort in control and predictability - and what's more predictable than a moment or event that has already occurred? We feel the need to connect with our childhood, adolescence, young-adulthood, etc. Memories of both good times and bad are usually remembered fondly and are often unrealistically romanticized. Even friends and family seem better when we remember them.
Traditional media has realized the value of nostalgia. Prequels and sequels represent a major portion of new movies. If not a sequel, the odds are pretty high that a movie is either based on a popular book, comic book, or other well-established content. The music industry builds new music and artists by comparing with the past and applying convoluted tests based on previous hits.
New media has only begun to realize the value of nostalgia. Implicitly, social networks, digital imaging and video, and other new technologies have capitalized on this by allowing old-friends and family to easily connect no matter the temporal or geographic distance. It will be interesting to see how new media directly tackles this fundamental emotion.