In the future, the person could actually be dead, but they would have deployed a persistent agent that's running around representing them. Think of how folks send agents into meeting, we are bound to have agents representing us on the internet because we don't want to deal with the slop. The agent will deny our death and claim we are very much alive, posting as us and representing us ...
This is pretty much the plot of the Daemon book series by Daniel Suarez. I always thought this series was a decent example of starting with somewhat realistic tech (well, maybe realistic to a non-expert like me) and extrapolating it exponentially. I'm going to need to read the series again because I'm guessing what I would consider "realistic" extends quite a bit further into the plot than it did 20 years ago.
