1. It is hard to compete against free, especially in education.
Adam Smith pointed this out a long time ago: "In modern times [as contrasted with ancient times] the diligence of public teachers is more or less corrupted by the circumstances which render them more or less independent of their success and reputation in their particular professions. Their salaries, too, put the private teacher, who would pretend to come into competition with them, in the same state with a merchant who attempts to trade without a bounty in competition with those who trade with a considerable one. . . . The privileges of graduation, besides, are in many countries . . . obtained only by attending the lectures of the public teachers. . . . The endowment of schools and colleges have, in this manner, not only corrupted the diligence of public teachers, but have rendered it almost impossible to have any good private ones." -- The Wealth of Nations, Book V, Part 3, Article II (1776).
Thus the only way to compete effectualy against the current system is to offer something free-to-the-user as part of the mix. The current system of public schools in the United States gains revenues of more than $500 billion dollars per budget year for government-operated elementary and secondary schools.
http://www2.census.gov/govs/school/09f33pub.pdf
The blog author seeks to sell products for money to schools, and decries Khan Academy being provided directly to learners for free. Many other providers of educational products and services are doing what is REALLY hard: providing products and services to primary-age and secondary-age learners directly, on at least a cost-recovery basis, attempting to show a value proposition for products and services that families have to pay for after already paying their taxes.
Moreover, the monopoly or oligopoly the government-operated schools have on offering certain kinds of educational credentials ensures that Khan Academy and all competing providers of educational services have to rely on more than just price to win over users.
2. It takes guts to be an entrepreneur.
For anyone attempting to sell a product or service, the first challenge is competing against everyone else providing a product or service (including consumers who do it themselves). One of the entrepreneurs I most admire in the educational products space is a homeschooling materials supplier that has for more than a decade hosted a webpage called "27 Reasons NOT to Buy [Our Product]."
http://www.sonlight.com/not-to-buy.html
That takes courage and honesty. Rather than FUD, a stand-up entrepreneur lets prospective clients know what the competition offers. Clients are happier if they can shop and compare what's on offer from competing providers.
3. You can lead a horse to water, but you can't make it drink.
Khan Academy is provided over the Internet, entirely for free, but not everyone who has an Internet connection makes use of it. (Some readers who have commented here have suggested that the blog author should watch more Khan Academy videos before making a global evaluation of the quality of Khan Academy instruction.)
The public school system is free (that is, tax-subsidized) for all pupils, and the pupils are compelled to attend in default of government-approved, parent-funded alternatives besides. Even at that, teachers can't count on pupils being engaged in their lessons. It's not clear that providing this or that new lesson material will bring about more learning in a compulsory attendance environment, as another reader here pointed out while mentioning the interesting writings of the late John Holt.
4. Khan Academy leaves a lot of room for a better service.
I have watched SOME Khan Academy videos, including some of the most recently revised videos. My children have watched others. We have also done various Khan Academy online exercises. My homeschooled children's main online mathematics course is NOT Khan Academy, but ALEKS,
which to date offers much superior exercises (which are more like open-ended problems than mere exercises), much more relentless focus on steady skill development of learners, and a more complete and articulated curriculum for precalculus mathematics. I have urged the Khan Academy collaborators in past replies here on HN basically to reinvent the research ALEKS has done on knowledge spaces in K-12 mathematics
http://www.aleks.com/about_aleks/Science_Behind_ALEKS.pdf
and eventually to build a comparable framework to integrate all the Khan Academy exercises into a coherent curriculum.
Anyone can try out ALEKS for an unlimited number of free, time-limited trials. (I'm not paid to endorse ALEKS; I learned this from a local friend who telephoned the company and asked about this.) So you and the blog author and any member of the Khan Academy staff and any other person with an Internet connection can try out ALEKS and see what is like. What ALEKS conspicuously lacks compared to Khan Academy is audio explanations, and what differs from Khan Academy most conspicuously about ALEKS is that ALEKS costs money, but I'm happy to spend money on ALEKS for four learners in my family.
An even better source of videos on prealgebra topics than the Khan Academy videos are the Art of Problem Solving videos by Richard Rusczyk,
http://www.artofproblemsolving.com/Videos/index.php?type=pre...
also free and worthwhile for mathematical accuracy and engaging presentation, with very challenging problems. Art of Problem Solving links to other videos, some produced in-house and some from other providers,
http://www.artofproblemsolving.com/Videos/index.php?&
that are also very good.
Competition is good. I like the public school system, the lessons I teach locally as supplemental classes for advanced elementary-age learners, and Khan Academy and Art of Problem Solving and ALEKS all to be subject to competition, the better to have incentive to improve and to do better.
5. There will continue to be an important role for in-person teachers.
Khan Academy will not make in-person teachers become obsolete. I tell all my prospective clients for my own local in-person math classes about Khan Academy before the first day of each new term. A good classroom teacher, who knows the latest research on educational effectiveness,
http://www.amazon.com/Visible-Learning-Synthesis-Meta-Analys...
will take care to form a community of shared curiosity and reality checks on one another's thinking while teaching. There is an abundance of research on effective mathematics teaching,
http://math.berkeley.edu/~wu/Lisbon2010_4.pdf
http://math.berkeley.edu/~wu/Lisbon2010_2.pdf
http://math.berkeley.edu/~wu/NCTM2010.pdf
http://math.berkeley.edu/~wu/NoticesAMS2011.pdf
http://math.berkeley.edu/~wu/CommonCoreIV.pdf
http://www.aft.org/pdfs/americaneducator/fall1999/amed1.pdf
http://www.math.wisc.edu/~askey/ask-gian.pdf
http://www.ams.org/notices/199908/rev-howe.pdf
http://www.ams.org/notices/200502/fea-kenschaft.pdf
ftp://math.stanford.edu/pub/papers/milgram/milgram-msri.pdf
ftp://math.stanford.edu/pub/papers/milgram/report-on-cmp.html
and much of that research has yet to be implemented in most classrooms in the United States. It's even possible to compete with wholly free services and provide supplemental classes in mathematics that families pay for willingly and without compulsion. The key thing for a teacher to do is build a class that is engaging and that welcomes curious learners who are willing to challenge themselves.
See an earlier HN comment
http://news.ycombinator.com/item?id=2760663
for a bit more on the distinction between problems and exercises.
I wish the blog author, the Khan Academy developers, and everyone teaching mathematics well in spurring the development of better materials and teaching practices so that more mathematics learners learn more mathematics better.