I can't physically get to a funeral for everyone I now know. And that's too bad, because funerals are good for people. You need a way to memorialize someone, preferably by gathering in a place, and preferably with a strong ritual component, like the lighting of candles or the gathering around a gravesite or the recitation of formal prayers or sayings.

(Because ritual, among other things, is what we do when we want to say something heartfelt but unoriginal. It's unfair to force someone who has lost a friend to write a standalone obituary on a blog. There are a lot more mourners in the world than writers, you want to be able to mourn for people that you don't know well enough to memorialize in prose, and writing public statements of memorial is often not self-effacing enough. Your real desire is to call attention to your deceased friend, so it seems unseemly to risk calling attention to oneself instead.)

Good for Facebook for figuring a lot of this out. But there will need to be more of this, because you're right: The web, and our network of acquaintances on that web, is going to outlive us all.