It is difficult to imagine the great volume of data we supply to different agencies in our everyday actions, bit by bit through surfing the Internet, posting on social media, using credit and debit cards, making online purchases, and other things where we share information about our identity.
There are infinite ways to slice and dice data, which itself is quite daunting as at every step, there is potential to make huge mistakes.
http://www.thehindu.com/opinion/op-ed/how-to-handle-big-data/article22745327.ece
