Though Facebook started out as a network for college students, its appeal has reached users of all ages. "People over the age of 30, that group is actually the fastest-growing group on the site," Mark says. "People are even using it to connect with President Obama. He has the most connections out of anyone on the site—almost 6 million. He was using the service throughout his campaign to give people updates about what was going on with the campaign. Even now that he's in office he's using it to connect with supporters about the different packages he's trying to get through."
For adults, part of the Facebook's appeal is that you can easily control who sees what and whom you are friends with. Mark says this is a crucial aspect to the site's success. "One of the biggest differentiators between us and other services is people have complete control over how they share their stuff online, " he says. "You can take a photo album if you want and just share it with the people you went on vacation with. ... Most people don't want to share a lot with a lot of people."