Yes @anon76657042, you make lots of valid points, and for sure some fields of IT - like search - will be very hard to decentralize. Also decentralized systems tend to become more centralized over time, like the often mentioned example of email. While email is inherently decentralized, people have flocked en masse to using Gmail, because of its spam protection or just convenience, and effectively centralizing it.
The core protocols of the internet like TCP/IP and DNS are decentralized, the centralization happens in the upper layers of the technology stack. Here the monopolists drag you into their walled gardens - vendor lock-in results - making it really hard and costly to ever leave once you are invested. And you are subjected to the rules of the provider, which may change at any time (like e.g. FB news feed algorithm recently). They may even decide to shut down your business on a whim if they so decide, block you from their network… which occasionally occurs.
For decentralization to be successful there is a need for more decentralized, federated protocols to become standardized and widely adopted. While this is against the interests of the monopolists, it would open up the markets giving more chances for smaller players to actually succeed. Currently you have innovative startups that are just targeting to be gobbled up by the big players for a couple hundred million dollars, after which the founders either take a position in that company or move on to a new startup venture.
There have been interesting discussions on Hacker News that companies like e.g. Google are not all that innovative anymore (except in some specific areas, like AI) and just buy up the competition. Thereby stifling overall innovation.
Even the recent Cambridge Analytica scandal may eventually be to the benefit of Facebook. Mark Zuckerberg has apologized and said FB is open for more government regulation. This regulation - when it comes - will not be targeted to a single company however, but all across the board. FB - as large as it is - can easily afford dealing with this, while small startups will have a much larger struggle to comply (see: TechCrunch: Regulation could protect Facebook, not punish it and techdirt: How ‘Regulating Facebook’ Could Make Everyone’s Concerns Worse, Not Better).
Like you, I hope there will be more competition amongst centralized IT competitors as well, with preferably different business models, like subscription-based rather than ad-based models. Have users become the customer again and good privacy policies and ensurances in place. Its just that current monopolists are so incredibly entrenched, having revenues larger than many individual countries and just growing ever larger, which will make this harder and harder.
Now, decentralization based on good standardized protocols give you choice and interopability, avoiding walled gardens. As an example: The W3C last January made ActivityPub a recommendation - a decentralized social networking protocol. Already a number of open-source projects are creating new social networking apps based on it, or are rewriting their stack to support it.
A notable example here is Mastodon (“Social networking, back in your hands”) - a decentralized microblogging network comparable to Twitter. With Mastodon anyone can spin up a server and attract users to it. These micro communities are self-contained, but users can decide to follow users on other servers, thus creating a larger interconnected network structure. Unlike Twitter - where you have a single moderation policy - on Mastodon every server can set their own rules, topics and guidelines and you are free to choose based on your preferences.
Note that Mastodon - based as it is on ActivityPub - interoperates with other software products, something you won’t find e.g. between Twitter and Facebook.
Setting up a server - while requiring some knowledge - is not all that hard and does not require you to have intricate knowledge of database management and such. This is all managed by the application, which is open-source and has more than 450 contributors as of now and many more people watching and reviewing the code.
I think the argument of “all hubs” being compromised by governments or otherwise foul actors doesn’t hold much sway (in fact this argument is often used in scare-mongering tactics against The Decentralized Web). Sure, a server can be compromised, but so can the servers of a centralized application provider. I believe American companies (and any company doing business or hosting server in the USA) are already required by law to provide backdoor access to their information to government agents, like the NSA, or at least there is regulation like this in the works (there are even conspiracy theorists that claim that FB was founded by the CIA - which I don’t believe, but it is not impossible).
Large social networks may be just as vulnerable to attacks, riddled with zero-day exploits in closed-source services, and big companies like Yahoo and LinkedIn have been hacked already leading to millions of accounts to be stolen. This has arguably a much larger impact than having to hack each individual decentralized server or even individual user accounts (depending on how encryption policies are applied).
Note that there is a form of decentralization that goes even deeper than a federated system (like Mastodon) that needs servers (or ‘hubs’), and that is a fully distributed, peer-to-peer system where every device is both the client and the server. Our laptops - and even our smartphones - have become very powerful computing platforms that are up to this job. Example implementations (earlier mentioned by me in this thread) include Dat Project, IPFS and Beaker Browser (based on Dat Project). Beaker allows you to host your own decentralized website, and as people visit your site, it will get more peers hosting it, thereby increasing performance and availability. Very interesting.
ActivityPub and other decentralized protocols offer new opportunities to companies, new business models. Like any commercial entity they can ensure they operate with integraty, good ethics, and have good compliance regulation in place, certifications, thereby gaining the trust of their user base. There is huge innovation in encryption technologies, not just in encryption of data, but also in having strong authentication and digital identities (see for instance Rebooting The Web of Trust, here and here).
In short, I think, The Decentralized Web has the potential to become the web of the people again, rather than the playground and cash cow of the few 
Thanks for your views