Usually I'm the one reaching back that far, sometimes on Classmates.com or things like that, often with sad results.
In the early days of the Internet I tried to find a girl I used to know, but her married name was so common it took weeks. When I finally reached one of her relatives I found out she'd killed herself seven years before. This happened again with another woman, so I decided to give it up.
Anyone googling my name is apt to find me in the top five. Recently, I've been contacted by someone I hadn't heard from since 1984 and a week later by someone I hadn't heard from since 1974. Usually this sparks a flurry of clever emails. But the 1974 person and I are planning to meet for coffee.