Sometimes, the reason has been changing technology. Sometimes, opportunity. Sometimes, competition. Sometimes, government antitrust pressure.
Whatever the cause, AT&T; has been a corporation in an almost constant process of reinventing it self ever since March 3, 1885, the day Alexander Graham Bell's American Bell Telephone Co. incorporated it to take over a burgeoning long-distance business.
And while analysts who follow the telecommunications business are agreed that yesterday's surprise announcement of plans to break the firm into three separate companies is one of the most breathtaking make-overs yet, no one believes it will be the last.
"I wouldn't dare say this will be the last restructuring of this company," said Douglas A. Christopher, an analyst for Crowell, Weedon.
Keeping pace with changes
"If you look at the speed at which telecommunications technology changes the market, and then the changed telecommunications market turns around and forces a change in the technology, perhaps the most important thing they've done with this announcement is give themselves the flexibility to make more changes to keep pace," Mr. Christopher said.
"We're talking about $75 billion in revenues -- there are lots of household-name companies out there that have $1 [billion] or $2 billion -- and if you look at this enormous entity, there are still a lot of ways to break out huge companies from it, or to reorganize it internally to respond to this changing environment," he said.
That is not a new story.
By the 1890s, with Bell's original patents expiring and smaller competitors swarming onto its turf, AT&T; was into its first self-reinvention, taking over its parent American Bell companies in 1899 and setting out on the path that made it "Ma Bell," the dominant force in the U.S. telecommunications industry for most of this century.
In 1907, J. P. Morgan and his allies took over the company and installed Theodore Vail as president. Mr. Vail built the company based on an essentially simple strategy -- getting federal and state laws passed that made telephone service a monopoly utility, and buying up as many smaller competitors as possible.
When the administration of President Woodrow Wilson threatened antitrust action, the company agreed in 1913 to sell off Western Union, the telegraph company it had taken over in 1909, and to buy no more independent phone companies without regulatory approval.
Mr. Vail's basic strategy held for four decades, the longest stretch in the company's history without gigantic restructurings.
But in 1949, AT&T; faced a Justice Department lawsuit aimed at forcing it to sell Western Electric, its phone equipment manufacturing arm. A 1956 settlement of that suit let AT&T; keep its grip on Western Electric but required it to agree never to enter any other unregulated business.
A string of government actions followed, including two that forced AT&T; to give up its phone equipment monopoly in 1968 and allowed new carriers such as MCI to hook their microwave systems into the phone network in 1969.
Then came the Big One, the government suit that forced AT&T; to agree in 1982 that by 1984 it would spin off the seven regional "Baby Bell" companies, keeping the long-distance network and Western Electric to itself.
Since that 1984 spinoff, several of the regional Bell telephone companies have become some of the most aggressive and innovative businesses in the United States, but AT&T; has seemed to meander in search of a new identity.
In 1990 it went into the credit card business with the Universal Card. In 1991 it took over computer maker NCR and took a majority interest in computer maker Teradata.
The company thus became at a stroke the world's No. 7 computer maker, but it never turned that acquisition into a strong profit producer.
"The problem has been that this is a company that has not been organized in a way to make it creative, and it exists in an industry, telecommunications, that is a focal point of some of the most creative and dynamic changes going on in the world today," said Kevin Cory, an analyst for Ferris Baker, Watts Inc.
"When you look at the components they have -- a big computer company, long-distance and international networks -- you have to ask yourself why AT&T; has not been a participant in the telecommunications boom," said Crowell Weedon's Mr. Christopher.
"Clearly, they asked themselves this and decided that they were badly set up to compete and needed to get back to their core businesses," he said.
Said Mr. Cory of Ferris Baker Watts: "Given what's happening to the stock price today, it appears that the market agrees that they've now designed a structure that will allow them -- maybe force them -- to become pro-active managers in this tremendously dynamic milieu where they operate.