This argument is constantly trotted out (usually by Microsoft to try and
excuse their inability to write uncompromised software) and it is
certainly persuasive. But *only* if you consider the desktop market
alone. As soon as you look at the server market, the argument becomes a
lot weaker.

In the server market, Linux dominates. Not, it has to be said, to the
same degree as Microsoft dominates the desktop market, but it still
takes about 50% of the share, with other Unixes taking a large slice of
what's left. Microsoft has by far and away the minority share. And
yet, when the crackers go after servers, they *still* go after the
Windows servers.

Why? Because they are the easiest target, not because they are the most
numerous. If Microsoft took security seriously - and there is a
conspiracy theory which says they don't by deliberate design - then the
numbers argument would actually become true across the board as the
crackers would no longer have the incentive to concentrate on the weaker
target.