1. Abusive use of patents to prevent small upstarts that can't afford litigation
2. Getting regulations passed that are so expensive only established players can afford them.
3. Making visa requirements so complex and expensive that it becomes a competitive advantage to have an entire department dedicated to it in your largco.
Having so much money that you can put out a product that integrated better with yours is just another spin on putting out a great product as far as I'm concerned, and thus never worries me.
IMHO doing away with patents would do much more to "curb bad monopolies" than any litigious strategy.
If a site owner wants traffic on their site - and most do - they want to make their site as easily discoverable as possible. That means being in all the search engines. Blocking one engine (or all except one) flies in the face of most business models.
The only exception I can think of is Google properties. By blocking out competitors, they can try to worsen the experience on other engines. Like imagine a video search on Bing that didn't include YouTube? But even then, it seems like someone finding a Google property via Bing still furthers their interests.
Related, "Please Don't Block Everything but Googlebot in robots.txt": http://danluu.com/googlebot-monopoly/
Odds are the more troublesome scrapers are probably ignoring robots.txt anyway, so I wonder how useful it is.
I use Bing as my default search engine, but it falls short of Google's results for a lot of programming-related queries. I still end up having to use Google a few times per day when I'm working.
That said, DDG is damn good at giving me relevant stuff on clear queries. But i find that Google and DDG alike gets into a bind if i get a bit technical.
There is also startpage.com (!s(tartpage) in DDG) to give anonymized Google results. And also ixquick (!ix(quick), natch) for a meta-search (not sure exactly what engines they cover).
I am as skeptical as anyone about giant corporations, but this is a stretch. How and why does our society expect players to refrain from using their current position to advance to a better position?
Note that I'm not talking about some clever algorithms or UI or any other kind of actual innovation. All that stuff is solely "capital" they could accumulate due to their existing power and reputation, but which gives them a huge advantage. A startup, no matter how genius their algorithms are, couldn't beat them in that field, simply because they don't have those resources.
Of course you could say "so what, that's the free market" - and of course building capital is a normal post of business - but when this inequality is so severe that it makes competition practically impossible (or only possible between 3 or 4 well-established players, as we see now) then I'd argue that something sounds be done.
But isn't that what the essence of competition is, in the search engine market?
Unlike switching from Facebook, you don't need to get all your friends to come along. Unlike switching from GMail, you don't need to move a bunch of data. Unlike switching your company away from Windows, you don't need to buy all new software, retrain all staff, or get your partners to change the format they use to interchange data with you.
If someone were to build a better search engine, we would all just switch. Like when everyone left Altavista in 1999.