Since I run Killed by Google, I feel it's important to clarify that the average Google product lifespan is much longer than four years thanks to flagship products like Gmail, Maps, Docs, etc. I can't actually get a solid number despite a lovely spreadsheet of products that I actively track because I haven't even compiled them all yet. Anyway, I made a choice not to draw stats in killedbygoogle.com for a reason, and it's because they're misleading to most people. When I'm asked about it, I say, "The products listed lasted an average of about four years." KBG is cynical view of Google's product strategy by any measure, but at least it's not drawing empty and misleading conclusions.