In case it wasn't clear, the way I define monopoly is synonomous with coercive monopolies. So I would not consider 70% marketshare to be a monopoly, and in most cases I would not even consider 100% marketshare to be a monopoly. Likewise, in the vast majority of the types of cases you're raising, I don't consider it to be a problem.

With US Steel and ALCOA, if these companies were in any way not serving the needs of the market, it would be perfectly feasible for competition to successfully enter the market. (Maybe that's what you're saying too.) Assuming they were not using government regulatory capture to prohibit the operations of their competitors (which, actually, is practically universal these days, and is precisely what I do consider to be a monopoly).

Your redefining the term. In law, a monopoly is business entity that has significant market power, that is, the power, to charge high prices. http://en.wikipedia.org/wiki/Monopoly

While, I get where your coming from. If you want to redefine a term use a new word, I would suggest Monopower if you don't want to say coercive monopolies.

PS: The reason you don't need 100% market share to count as a Monopoly is once your competition can't meet the full needs of the market so you can increase prices which in theory causes a loss of market share, significant barriers to entry can dramatically slow this process down. If the barriers to entry are high enough you can fluctuate between high prices -> slightly below market prices -> high price to prevent the competition from affording to expand quickly or even drive them out of the market as they must conserve cash to survive your dumping product on the market.

I'm not redifining the term, economists are. Here is an etymology from dictionary.com

monopoly : "exclusive control of a commodity or trade," 1530s, from L. monopolium, from Gk. monopolion "right of exclusive sale"...

The people who have started using "monopoly" to mean "significant market power" and the like were doing a bait-and-switch to try to further an anti-business academic or political agenda. And most of the arguments you hear using the word "monopoly" imply the older definition that I'm using, but apply it to much looser definitions. For example, MS was never even remotely close to having a monopoly on operating systems. In fact, such a thing is not even really fathomable.

PS: The reason you don't need 100% market share to count as a Monopoly is once your competition can't meet the full needs of the market so you can increase prices which in theory causes a loss of market share, significant barriers to entry can dramatically slow this process down.

I didn't quote your entire paragraph, but I'm referring to all of it.

This kind of reasoning (which is reasonable and extremely common) is totally rationalistic (which is properly defined, by the way, as being an argument that seems deductively valid but is divorced from the way reality really is). I could talk about this at length, but I'd rather just give a short example for now. Imagine I'm a big business. If I'm consuming a particular kind of product as an input to my production, and one particular supplier charges a very high price, it wlll be greatly to my interest to either invest capital to produce it on my own, or (much more likely) seek out new producers to enter the market. If the existing supplier then tries to manipulate prices to drive the new competition out, only planning to raise them right after, I'll just see through it and continue purchasing from the new producer. A group of companies in my industry could even come to a mutual agreement of this sort to ensure that new competition enters.

The point is, in a capitalist (that is, politically and economically laissez-faire system), people don't just keel over when there are problems in the market, if those problems are actually big enough to be worth solving.

By the 1530 definitive it's the ability to control not the act of control. Historically, governments have granted monopoly's for various activity's, that did not mean someone needed increase prices just that they had the ability to do so should they chose. Obviously after being granted the power most chose to exercise it and become weathly, but not all.

More recently manufacturing has enabled company's to create capabilities though investments that are not easy to duplicate.

Intel is the only company on the planet capable of manufacturing 22nm chips at scale. Other companies can do 28nm and given time other companies will catch up. But, their Monopoly on 22nm chips has nothing to do with patents and is dependent on the incredible multi billion dollar investments required to manufacture at such scales. 14nm Fab's are expected cost more than 5 billion dollars per facility, and vary few institutions can afford such investments. http://www.kitguru.net/components/cpu/carl/intel-plan-fab-42...

PS: In 5 years 22nm manufacturing will be yet another commodity process, but by then Intel will have moved on. Intel has no interest in becoming a true monopoly, in large part due to the legal limitations that monopoly's face. However, that does not mean if the law was revised they could not rapidly do what Standard Oil or Alcoa did.