British Airways, explained in post #57.
Numbers don’t matter so much as leveraging what power you do have in an anti-competitive manner. Of course the bigger the numbers you have, the more power you tend to have, so such practices tend to be found in the 50%+ group.
For example, Apple is acting in an anticompetitive manner against Psystar, trying to not allow competition. Yes, I know the judge denied that. But their monopoly is a legal one based on the limited granted copyright monopoly Apple has on OS X (the extent of said monopoly still to be decided).
It’s like if you invented a revolutionary optic mechanism for a rifle scope and sell a scope based on it. You’re a small part of the market, but 100% of the market for scopes with your mechanism. Your patent on it keeps out the competition legally. BUT, if you manufacture and sell that part, you can’t keep others from making scopes based on it (your rights were exhausted at the time of sale as with, IMNSHO, copyright). Selling the part but still trying to keep others from making competing products is anticompetitive.
There is no such thing as having a "monopoly" on your own trademarked product. Simple as that.
"Monopoly" applies to a marketplace. A company may act in an anti-competitive manner, in a given marketplace. But it's not their own product that's at issue, it's the position of the company in the marketplace and how they act about it.
If I invent and trademark a "Dayglored Widget", and defend my trademark (something I have to do to keep it, ya know), am I a "monopoly" because I'm the only manufacturer?
If I sue someone who -- illegally, in defiance of my legally binding license -- makes work-alike widgets that copy trademarked features of mine, am I a monopoly because I defend my legally-protected product?
This is silly. Really.
I see where we disagree. Let me try to explain.
Microsoft does not manufacture "computer systems". They make software. Part of a system, but only half.
Dell and other PC hardware vendors do not manufacture "computer systems". They make hardware. Part of a system, but only half.
Show me a Dell computer that consists of Dell hardware integrated with a Dell operating system. Ain't none that I know of.
Show me a Microsoft computer that consists of Microsoft hardware integrated with Windows. Ain't none that I know of.
Apple manufactures SYSTEMS, consisting of hardware integrated with software. They make SYSTEMS. They do not sell their software for use with other manufacturer's hardware, and while they ALLOW -- under certain circumstances -- Mac owners to put other software on the Apple hardware, they NEVER sell the hardware without the software. They sell SYSTEMS.
When will the Psystar apologists realize that Psystar is not making a competing product (a system) -- they are making an illegal copyright-infringing piece of hardware and encouraging Mac-heads to violate the terms of the OS-X EULA (which states you may not install OS-X on non-Apple hardware).
The reason that restriction is legal is simply that Apple manufactures and sells SYSTEMS and they have the right to require that the SYSTEM not be broken up in pieces.
There's lots of precedent for that. Analogies with Windows and PC hardware are fallacious and nothing more.