Earlier quoted context omitted.
"Big 4" used to refer to accounting firms. Accenture used to be a part of the "Big 5" with Andersen, but they had to re-brand because of the Enron scandal. They no longer do accounting. But now all these companies are bleeding over into each others business areas - many do strategy, operations, implementation, accounting.
another minor nitpick-- Arthur Anderson had just recently spun off its consulting division as Accenture before the Enron scandal hit, not in reaction to it. It was a move that had been planned for some time. And I'm sure they thanked their lucky stars they completed the spin-off before Enron; Accenture was safely insulated from the fallout that absolutely killed Arthur Anderson.
All Big4 firms had to shelve their IT consulting to separate divisions or into new companies which most later sold:
Arthur Anderson formed Anderson Consulting which later became Accenture.
Ernst Young - Ernst & Young Consulting which was acquired by Capgemini
PriceWaterhouceCoopers sold to IBM Global Services
Deloitte retained its consulting division I think
KPMG - KPMG Consulting - Bearingpoint?