Mirror Internet? Yeah sort of like that Star Trek episode "Mirror Mirror" where Captain Kirk was evil and Mr. Spock wore a goatee. Where everything was flipped upside down. Good was evil and evil was good. Imagine the Internet, now imagine a flipped over Internet, a Mirror Internet called a Darknet.
Wait, what exactly is a Darknet? It is an alternative to the Internet and not available from the Internet but uses the same or almost the same technology. It is something that is being developed.
Using an Internet MEME with Bender from Futurama I can better illustrate with satire and sarcasm what this Darknet might become. It will be a private Internet that one can join and have no government regulation, it will be full of free MP3 files, pirated files, DRM-Free software and other things. Yes it is being worked on, and yes it is not fully compete yet.
Why is it growing more and more popular? Well as governments regulate the Internet more and more, bring about censorship and get rid of being anonymous and basically take away rights, freedoms, and liberties the Darknets avoid all of that and create an adhoc network of peers, and IP addresses not available on the Internet for security reasons, and domain names not accessible on the Internet as well, plus web sites and lots of storage that cannot be accessed by the Internet.
Basically this is an old trick, back in the Arpanet before the Internet there were Darknets that were off Arpanet for security reasons. Many corporations have Intranets which are almost the same thing, the difference being the Darknet is not owned by a corporation and run by individuals as a hobby of sorts to share data and files and other things that the Internet would not allow. Since it is not technically the Internet, it is not subject to the rules of the Internet.
It has not yet caught on because nobody has figured out a way to make money on it yet. Most Darknets are run on a volunteer basis by people who donate their time, money, and resources to run it. Those people don't want the Darknet used for illegal means, but still want their anarchy or whatever so that they have their freedoms without turning into what they hate most, a fascist state.
I suppose there will be startups who want to invent technology for the Darknets to use, and a payment system (Bitcoin?) to pay for access to it, and software to hook up to a Darknet and keep track of bandwidth used and make autopayments.
What already exists? Meshnet is one such project, Reddit users click here for more info. There is software being developed call CJDNS that will allow your system to connect to a Darknet or one like Meshnet. Another Darknet is Hyperborianet that you can connect to and try out.
Note that some Darknets got taken out because they traded in child-porn, groups like Anonymous went after them. This has caused some concern about setting rules for a Darknet, and most supporters are anarchists that don't want rules, but have to implement them anyway. Most don't want illegal activity such as piracy, but cannot prevent it. A system might be made to ban IPs from Darknets for violating rules.
Some people at Microsoft figured out that Darknets would defeat DRM long ago. Darknets are usually run by Ethical Hackers and they see DRM as unethical so they seek to remove it from software used on their Darknet.
It is painfully obvious that for any Darknet to be successful it should follow a set of rules or ethics, and anyone who violates those rules can be banned or disciplined. For example no child porn should be allowed. In order to enforce that there will need to be a reporting system and people who are paid as administrators to carry out bans or disciplines in some way. In order for that to happen the Darknet has to have a paywall in order to fund their own administrators to keep order on the Darknet. After a while the Darknet will resemble the Internet in the way it is managed, except that instead of a government regulating things it will be a group of paid administrators. That is where the startups come in with business models, software, and services.