I think the diversity of opinions on this thread show that "Big Data" is just another magic marketing word that means whatever you want:
"Buy our server to support Big Data"
"Buy our professional services to implement Big Data"
"Buy our DBMS to support Big Data"
"Buy our software to manage, analyze, etc. Big Data"
Or at a lower level:
We have "Big Data" = We have "Big D***s"
BINGO
There have always been and always be large information stores. Increased technology simply allows some of that data to be used in faster more pratical ways.
If a new term helps to create dialog in the C-Suite as to what the REAL needs for data are and what practical and competative purpose they serve then fine, but otherwise it once again marketing driving technology needs.