I don't know, I'm starting to change my opinion of this. I used to think 'big data' meant anything that didn't fit easily into a RDBMS. At least petabytes.

But, more recently, in conversations with non-programmers, I see that 'big data' to them, means 'broad data' - it means trying to track everything possible and make sense of it. The average business user is really excited to be able to cross-relate disparate types of data - in an effort to make things better. 'Big data' enables the breaking down silos and enabling of cross references. It's about making empirical decisions based on data rather than opinion or intuition. That's really good, in my opinion.

So, 'big data' in that way is more amorphous than just the size of the data. With services and networks, the question becomes where does the data begin and end? Big data is potentially everything.