There's nothing illegal about a company holding a monopoly. There's plenty illegal with a company abusing a monopoly -- dumping product below cost to get a competitor out of a market, only to be able to jack up the prices, for instance.
Should the government not have stepped in against AT&T? Look how far long distance prices have fallen since the consent decree. AT&T's monopoly was quite strong -- they took Microwave Communications, Inc., better known as MCI, to court for years in the 70s or so to keep them out of long distance. Or would you still prefer to pay $.30 and $.40 per minute for long distance, 24/7?
The point of anti-trust is not to "oppose free enterprise" -- it's to protect it. Market capitalism depends on markets absent of externalities, markets that actually work. Illegal monopolies hurt consumers, unfairly hurt competitors, and actually retard economic growth.
I guess no one remembers MS's anti-competitive and illegal "break it" behavior with DR-DOS in the early 90s? No one remembers the death of WordPerfect and Lotus when MS gave their own Office team the source code for Windows 95 six months before their competitors?
What about this past week, when MS back-pedaled on its "willingness" to let mfgs. decide what's on their desktop? "You can't put AOL's icon unless you put MSN's on too," they told Compaq. And that was in the one area where MS "gave in" to try to win a settlement. Where does this end?
I like MS products too. But that doesn't mean they haven't broken the law, and that doesn't mean that they aren't a dangerous monopoly.