Incremental reading is an attention destroyer
Criticism
In incremental reading, it is very important to make the right choice of the learning materials as they are often unsuitable for incremental processing.
Tomek wrote:
It is possible that article structure and quality do matter that much because the real learning bottleneck is the human brain (speed of cortex plasticity)? What if you can only absorb X items of knowledge each day -- if you try to do more, you do something bad to your brain? Here's one idea: If you overload your brain with new stuff, it won't have the time to form meaningful connections between the things you know, so your knowledge may be reduced to the ability to answer gameshow-like questions.
Solving any significant problem requires periods of prolonged concentration. I fear that an information addiction (200 new tidbits per day) leads to attention deficit. Your brain is used to getting something shiny and new every 15 seconds (a new tweet, new funny pic, new headline, etc.), so when you tell it to work on one thing for 4 hours, it doesn't listen. I think I was able to concentrate more on one thing in times before Web surfing.
So, to put a tabloid spin on it, incremental reading could be the ultimate attention destroyer!!!
Hints
You are right about attention, memory bottlenecks, "meaningful connections", etc. However, you probably never tried incremental reading beyond theoretical description? Comparing it to Twitter or Facebook as used by Internet junkies is very inaccurate! The reward in incremental reading is based on quality learning, not "something shiny or something funny" (although, it will also depend on your personality and discipline as nothing prevents "shiny/funny" things to be imported to SuperMemo).
Answer
Your reasoning is largely correct, however, your ultimate conclusion is wrong. When employed along the recommended rules: incremental reading should dramatically increase your attention (as explained in the article on the principles of incremental reading; the Attention section).
Learning speed bottleneck
Cortex plasticity is indeed the bottleneck in the learning process. All speed-reading and speed-learning efforts may go to naught if you do not employ spaced repetition, which ultimately determines the speed of establishing long-term memories. Remember that in incremental reading, the volume of the material may be very high, however, the ultimate number of items entering the learning process, in the ideal case, is relatively small (usu. 10-20 per day, not 200!). It simply takes lots of time to fish for golden knowledge that will bring best value in the long term.
Overloading memory and the role of sleep
The existence of the memory bottleneck is the direct consequence of the second concern you raise. You can overload your learning process with excess information, however, you are unlikely to "overload your long-term memory". The process of forgetting and garbage collection executed in sleep have evolved precisely to prevent this problem. However much you try to learn excess facts, forgetting will clean up the excess, and memory optimization in sleep will ensure you develop all necessary "meaningful connections". Naturally, this will happen only if you get all sleep that you need (i.e. avoid using alarm clock, sleeping pills, staying up late, etc.).
For more see: Neural optimization in sleep
Learning vs. problem solving
You are right that solving problems requires concentration. However, in the ideal world, you should devote separate time slots to (1) learning and (2) problem solving. In Covey terminology, your learning boosts the Production Capacity, while your problem solving time is your Production time. Naturally, you can marry the two slots when problem solving occurs in conditions of information deficit. Incremental reading is an ideal tool for such situations. You can combine the inflow of new information with creative efforts and problem solving while retaining maximum focus on the problem at hand. This is explained in the section Creativity (the association bonus) of the incremental reading manual. You can optimize the degree of monothematic focus by using various tools of incremental reading, esp. Search&Review as well as branch review.
Internet addiction
Internet distractions can indeed be true focus destroyers. However, this is more a matter of self-discipline than an inherent problem associated with SuperMemo. It is up to you to decide if you wish to stray to Facebook or Twitter. Incremental reading may encourage a degree of straying (e.g. to import supplementary material from Wikipedia and/or dictionaries). The whole concept of the priority queue was developed precisely to counteract the cost of such straying. In incremental reading you stray, import, prioritize and ... forget (about the excursion to the web). The whole process can be under your rational control and the web may become an ally rather than an enemy.
Metaphorically speaking, an Internet junkie is constantly distracted with shiny titbits, while incremental reader focuses on fishing for golden knowledge.
Incremental reading boots attention
Incremental reading increases attention by letting you focus on a manageable portions of knowledge without feeling overwhelmed, without straying, without getting stuck on harder material, without worrying that you might miss important pieces when speed-reading, etc. Your best way to experience that improvement is to try incremental reading. However, you should know that the effects will not be instant. You will need to invest a lot of time in learning the tools, and then even more time in honing your strategies and learning about your own memory and reasoning. Few incremental readers become truly enthusiastic in their first year of learning.
Here is the quote from the incremental reading manual:
Incremental reading widely stretches the span of your attention. You will notice that a single paragraph in an article may greatly reduce your enthusiasm for reading. If you stumble against a few frustrating paragraphs, you may gradually develop a dislike of reading a particular article. You may even become fed up with reading for the entire evening. Incremental reading makes it possible to immediately move on to other pieces of information reducing the negative impact of frustration. It also makes it possible to split larger pieces into less intimidating portions. It allows you to read interesting bits before reading the boring bits. Those measures dramatically increase your attention. They also make reading fun. A skilled incremental reader is likely to develop an addiction to learning with all related benefits!
Article quality matters in learning
In incremental reading, you will quickly develop skills needed to instantly differentiate between high quality articles and articles that are full of fluff and wasteful prose. You will indeed fish for catchy headlines, meaningful sections, minimum off-topic commentary, etc. Article quality will determine your ability to employ speed reading, and to quickly prioritize your material. This has nothing to do with instant gratification obtained from social media, instant news, and other net distractions.