Facebook is generally for the alive ones. Now there's a new Unique Facebook Application which enables users to say R.I.P (rest in peace) to those who have passed. Everyone can add their beloved lost one due to the natural life - death cycle and then share the page with their Facebook friends so they can come say "rest in peace". URL : apps.facebook.com/fb-rest-in-peace/
I dont really think an app can give somebody the dignity they deserve in death, i think its creepy and just clicking an RIP button is no substitute for any of the measures we take after somebody dies.