I am sorry but I don't get what BIG data is. Is the BIG-ness due to the higher availability of data, its huge volume, it's implication (as Chris A. says) on overturning the model-led approach to science, its ability to help make businesses become better at building products and delivering services, its ability to help us see the big picture (as IBM's Jeff Jonas says)...or all of the above?
The other elements you mention - implication, new models, new decision making approaches - all flow from this abundance of data. I intentionally selected PW Anderson article "More is Different" as our opening article this week. Increased data quantity requires new approaches (and Hadoop and MapReduce evidence this).
I'd like to hear thoughts from others - do you agree with data quantity as the defining attribute of big data?