We are clearly in the early stages of a "tectonic shift" in the database market, as eWeek terms it. Not because any particular database vendor decided that the world was ripe for a change, but because the nature of data we're generating and processing has changed.
It is well understood that the current database giants have written superb products to solve primarily one problem (automating standard business processes), but we no longer live in a one problem world. The proliferation of mobile devices is forcing an immense structural change as we increasingly overlay a digital existence on top of our analog existence. If we can measure it, we can manage it; has transcended the world of business process automation and now has meaning in everything we do, as everything we do generates data. Driving, tweeting, gaming, friending, browsing, walking...it all generates data. We can capture, analyze and derive tremendous value from that data, but only if we can use low cost, high-quality data management products. This is the challenge MongoDB is laying down, and it is the challenge all other data management players must rise to meet if Big Data is going to realize its potential.
I've called out before that NoSQL and Hadoop are the new normal in data management. This is why. And it's why as much as the RDBMS establishment may wish it otherwise, the industry looks bright for NoSQL technologies like MongoDB.