According to Forrester Research, 55.6 million adults in the United States have a social networking account with a site like Facebook, MySpace or Twitter. More people join social networking sites every day. For some users, online networks serve as the primary means of staying in touch with friends and family. Social networking sites let us post our thoughts, pictures, videos, music and other content. But what happens to all of that when we die?

It's a sobering problem. As we invest more of ourselves into our online presence, we become more affected by the things we see and do on the Internet. We also affect our online friends. It might seem like worrying about what happens to your online presence after your death is a trivial matter but it's becoming more important as time goes on.

Part of the reason for that is the Internet provides a place for people to express thoughts and feelings as they grieve a loss. Your social networking profile could become a spot where your friends and family can share memories of you. People who might not otherwise hear of your passing may learn of it through your profile page.

But maintaining a presence online after you die has its share of problems as well. Mean-spirited people -- called trolls in the online world -- might take the opportunity to leave insulting or inflammatory comments on your page just to stir up trouble. Who guards your profile after you're gone? Can someone request access to your accounts to act as custodian to your online presence?

The answer varies from one site to another. As of yet, there is no law in the United States with rules about how to handle an online presence after someone passes away. Each company creates its own policies. Some, like MySpace, do so on a case-by-case basis. Others, like Facebook, establish rules that allow friends and relatives to transform a normal profile into a memorial.

Next, we'll look at Facebook's approach to handling the profile of a deceased user.