"One question begged of Big Data has been – is anybody actually handling data big enough to merit a change to NoSQL architectures?"

Prediction:

There's going to be a fuck-off huge market for helping later-stage startups bring order to their NoSQL databases and move that data into a more useful format.

Sounds like a business plan to me. Migration software to move data from MongoDB back to Oracle (or PostgreSQL, or SQL Server, or whatever)