I agree 100%. You should be continuously delivering in a way that allows you to learn about the area of greatest risk. For much of what Agile development is a

I agree 100%. You should be continuously delivering in a way that allows you to learn about the area of greatest risk. For much of what Agile development is applied to, the greatest risk is market risk. You want to get something out to users as quickly as possible to see if your assumptions about your users and their needs are right. For google style projects, there is primarily technology risk rather than market risk. If you are trying to build something that is obviously useful but is perhaps impossible, it makes sense to focus on delivering working systems that allow you to see if your assumptions about technological limitations are correct.