The fact that there is a Google Graveyard does not imply that someone thought that every service that Google creates should last indefinitely. I view it more as a useful reminder of how frequently Google does this - a good idea if you're about to make something Google does part of your workflow or habits.

There are also some products in there that were killed in a fashion that seemed capricious and difficult-to-explain in terms of popularity, usage and continued cost to Google - notably Reader and Code Search.