[space-monkey]

Frankly, the great thing about leading edge datastore development right now is that it's all over the map. Many of them will fall off the map over time, but having a couple of additional models to add on to the current great RDBMS tools can only be a plus.

I imagine that a significant driver of datastore heterogeneity is that there are a number of very different in-house datastores that are supporting extremely successful commercial ventures. It used to be that "you don't get fired for choosing Oracle." Now that Amazon and Google, etc, have paved the way, it's much more feasible for a corporate infrastructure developer to try to find a way off of the high-dollar proprietary systems like Teradata.

I also think it's interesting to note that some (most?) of the largest scale commodity RDBMS users couldn't get close to where they are without something like memcached.