If Facebook is depressing now because of all the people getting married and having kids, it's going to really suck in a few decades when everyone starts dying.

EDIT: Yeah, a lot of people have one or two dead facebook friends, I have two myself, but how many friends do you have in total? Statistically you're going to outlive 50% of that number. Regardless of which social media conduit is prevalent at the time, the death frequency is going to get pretty grim before you add your name to the tally. If you're lucky, that is.