This comment captures a lot, perhaps not in the way Ken intended, but I feel compelled to respond.
Lets start with the thesis statement, "The web is not open and becoming increasingly less so."
On its face, this statement is not only false, it is painfully so. Sort of like saying the world is not round and becoming increasingly less so. To pretty much anyone they would say "the world is clearly round, and its impossible to change that." Similarly there is absolutely nothing standing between Ken, or anyone else, preventing them from building an entirely different "web" just like Tim Berners-Lee did back at CERN. So the definition of the word 'open' here clearly is needs some additional verbiage.
The next statement helps a bit, "It's driven less by standards and more by de-facto implementations. Soon we can get rid of the standards committee and just talk to the implementers of webkit to define the 'standard'."
This deliciously captures a debate that has raged for 30 years at least. "Which came first, the standard or the code?"
Back when I was young and impressionable, the debate was something called the "ISO 7 layer networking model" and "TCP/IP". You see the international standards organization had decided that the world needed a global networking standard, and so they got their best standards engineers together to come up with what they gloriously christened the "Open Standards Interconnect" or OSI set of protocols. Meanwhile a scrappy bunch of network engineers and hacker types were in this loose knit organization called the Internet Engineering Task Force who were building networks that spanned countries and they wrote code and brought it to the meetings and debated stuff that worked well and stuff that didn't work well, and then everyone went back and wrote more code, Etc.
The forces of evil ignored the IETF and focused on the ISO working groups, since the latter were making standards and the former were just playing around with code.
As it turned out, working code tended to trump standards, and a process of debating changes to the system using working code vs debate using 'it should/it might' as opposed to 'version A does/ version B doesn't' meant that changes got made to standards based on a convincing argument that had never been tried or experienced in practice. The result was that the OSI standards had a lot of stuff in them to avoid issues that weren't issues, and were missing responses to things that actually were issues.
A number of people found the 'code first, standard later' methodology superior for that reason. Assuming that the code was available and unencumbered by patent or licensing restrictions. The latter of course became a much bigger problem when the focus switched to the IETF and the 'big guns' started their usual games.
My first response is then, "open" means anyone can implement and contribute new stuff. And by that definition the web is very open. However, since the community favors a implementation model over a theoretical standards model the 'cost' to influence change is you have to write code, as opposed to making a good argument. And that disenfranchises people without good coding skills.
The second part of this screed is prefaced with this: "And I think even worse has been the wholesale discounting of plugins." Which speaks to the other side effect of "open" as in "we don't make any boundaries we don't have to."
From a mass adoption point of view, the more variability you have in an experience the harder it is to capture the larger audience. This is why cars and motorcycles are all driven in basically the same way, Televisions have 'channels' and 'volume' and browsers have an address bar and bookmarks.
The unification of the structure allows for mass learning and talking in generalizations that remain true without device specific knowledge. Can you imagine how hard it would be to write a driver's code if every vehicle had its own customizable UI and indicators?
So as a technology matures the variability is removed and the common practices are enshrined into the structure.
What that means in a practical sense is that if you're trying to push the envelope in such a mature technology you will face higher and higher resistance. However, you are always allowed to create an entirely new way of doing things.
This isn't the 'dark age' it's the post renaissance start of the industrial revolution. Except instead of widely accessible books we've now got widely accessible information and a de-facto portal for accessing it.