Caveat: Googler here.

One of the things that had been problematic at Google is the creation of many more products than are really needed, leading to the infamous Google Graveyard. One of the reasons I have come to like writing design docs for my ideas is that a lot of the ideas turn out to be crap when they get written out. Quite a few are good enough that they have already been done, or close enough, which my colleagues can then inform me of. This is a very lightweight way of trimming out useless projects.

And no, Reader wasn't useless. Different story.