Despite recent promises of aggressive expansion into the legal market by the Big Four accounting firms, many attorneys believe current attorney-client privilege and conflict of interest rules will prevent PricewaterhouseCoopers LLP, Ernst & Young LLP, Deloitte Touche Tohmatsu Ltd., KPMG LLP and others from posing a serious threat to the legal industry.

Others believe there might be a fundamental philosophical difference between the services provided by accountants and attorneys, creating a barrier to entry by the Big Four. Although Phillip England, a shareholder with Anderson Kill PC, believes a Big Four expansion into the legal services realm would be a welcome change to the industry, he told Law360 that the roles of accountants and attorneys are, by nature, a dichotomy.

"The basic role of an accountant is to take a concept that is intrinsically gray, and make it black and white," England said. "But the basic role of a lawyer is to make something that appears black and white, gray, so it can be subject to dispute and an ultimate resolution."

But if the Big Four are ultimately able to compete against BigLaw in the U.S., firms should watch out because they pose a serious threat to business, experts say.