I ask because a lot of things Google has killed is hard for us to replace. Eg, i don't want to try and build Wave, or continue with Apache Wave, etc. It's a big, complex problem. But a personal content aggregator like what i thought Google Reader was seems quite easy to implement.
In other words, why haven't we (public or startups) built the core functionality of Google Reader that so many appear to love? It seems like an eager and easy to reach market. What am i missing?