One thing that may surprise some people is that when students were allowed to choose how they spent time on the Khan site, they chose not to view the videos that established Khan Academy in the first place. They preferred to spend time "taking tests" than watching videos...yes you read that correctly. This is in stark contrast to the outcry from educational professionals that there should be "less testing".
What the less-testing crowd doesn't understand is the process of "Assessment AS Learning," the continuous feedback and challenge provided by the online experience both supports and motivates learning. Assessment of individual competencies is embedded in a "gaming" context, that provides an achievable short term goal. Working to get to the "next level" is fulfilling, even addicting (in a good way). And like with online games, individualized blended learning promotes students helping students in ways not found in a traditional competitive classroom environment.
The best computer/online games don't get in the way or provide too much help, it is often trial an error for the user trying to develop the skill needed to reach the next level, and that is part of what makes games addicting..."I'll stop just as soon as I figure out how to finish this level." The thrill of learning is in discovering something new or beating the challenge of a new skill. Games designed so that all users eventually succeed might monitor the user behavior and provide some redirection when absolutely needed, just before the user would give up. But most often, when games don't have 'intelligent tutors', the user will ask a peer, "How do you beat this level?"
Blended learning has an advantage over software-only-self-paced-learning, that a teacher has access to the data from each learner's online experience and can provide targeted one-on-one help that goes beyond what is built into the online platform. However, this is a new kind of professional practice in its infancy. Best practices must be defined and teacher proficiency developed in those practices. In the same way, online learning platforms can be improved over time by adding logic that knows when to step in with a suggestion such as, "You've tried that problem set 10 times. You may be more equipped to conquer this level if you watch this video," what video segment or activity to recommend, and when to trigger an alert to a teacher to intervene, diagnose, and prescribe an alternative learning path.