> There are serious logistic/economic barriers to enter
    > the search space.

But there were before Google started as well. Google entered the search engine party after it seemed to be over. I remember reading about them first on slashdot and thinking - wow - someone still thinks there's room to break into this? Surely portals are the proving ground. (Who knows? Maybe they are.)

Something particularly interesting about Google is that they just took the industry head-on. I'd guess that there'd be areas where you could build a kind of search engine that was better than the market leader, and focus on carving out a niche. Yandex have done just this with the Russian market. (and there's an example of a commercially-viable post-google search engine business).

But Google just went after being the leading power.

History in general, but in our space in particular, is written by small, well-coordinated teams who can repeatedly execute. If you can get that team together, you can do almost anything.

Just because it is expensive and technically hard doesn't mean Google is preventing them in any way.

What would be worrisome is if they abuse their market position. Is there strong evidence they do this in search? It'd be more concerning if they did to promote their other products.

I am refuting the statement "A monopoly should be defined by barriers to entry, not just market share." made by sfrank2147, specifically interpreted as "barriers of entry for search market", which are surprisingly high. Based on his definition, Google is deep into monopoly territory.

What a monopoly really is and whether Google qualifies is a separate question, and I'm recusing myself from commenting on this point.

> Just because it is expensive and technically hard doesn't mean Google is preventing them in any way.

I agree. It means it's a natural monopoly. These should be regulated, because otherwise there is a tendency for them to abuse their power.

Duckduckgo may claim otherwise.