meets this criteria but I would argue that part of Google's service are the ads which are not offered freely, i.e. they cost money.
Google is free for most users...
Google is a business. If they want fault tolerance then they can buy it from Akamai or else build their own global infrastructure. If Google disappears, we can get similar service from many of their competitors. They aren't part of the infrastructure of the Internet.
exist. But if DENIC ceases to exist, it is 100% certain that ICANN would find some other organization to continue offering .de nameservice.
What makes you so sure that DNS and/or ICANN will survive?
LDAP is a well-proven robust and scalable directory services technology that is deployed at large organizations world-wide. But even though LDAP can do everything that DNS can do, there is no movement at all to replace DNS with LDAP and very few organizations run their DNS on top of backend LDAP servers. So DNS will survive for a long time. But if DNS would be replaced by LDAP, then I think DENIC would provide LDAP hosting for the .DE domain. And if DENIC does not survive, then ICANN would find someone else to provide LDAP services for .DE. But if ICANN does not survive, then its powers of allocating top level domains will pass to another organization, and this organization will make sure that there is somebody to host .DE. --Michael Dillon