And this is as true online as off.
I still bear the scars from when we changed the forum tool at the BBC and, despite my best efforts to take folks with us, many still reacted as if I had walked into their homes and changed the lounge wallpaper. They were right. It was as if I had. And to be honest I wasn't that keen on the new wallpaper myself anyway ...
But whatever. The point is that if you have done things right then people have a high degree of ownership of online spaces. They invest in them emotionally let alone in terms of time and effort.
Given all this I found is surprisingly moving to read this open letter to "Whoever Controls The Fate Of FriendFeed" in which a user makes a plea to keep the servers running whatever happens to the service.