Interesting topic; I'll take a crack at it. And won't get into politics:

Your example of the world's banks is in fact well known - why else would US and Canadian banks be worried about the welfare of European banks? This isn't a hypothesis - it's reality.


There are more possibilities:

Virtually every country that has a semblance of democracy, has realized that monopolies don't serve the country or the people well. Consequently, they have enacted anti-monopoly laws (anti-trust in the US).

The financial interests of companies/corporations are best served if they have a monopoly. By the same token, this isn't in the interests of the general population of the country as it limits competition which we pretty all believe is a good thing for society.

If companies weren't involved in creating monopolies (or groups of monopolies) the legislation wouldn't have been required. My naivety level is low enough that I know they are still attempting to create monopolies one way or another.

Background - interesting reading - I had no idea the concept has been around this long:

http://en.wikipedia.org/wiki/Competition_law

Glenn