usually the definition is around some technology coming out that the incumbents were so heavily invested in earlier technology that they couldn't embrace the new technology until it was too late. It's not that taxis companies couldn't have developed tech, it's because they followed the law which caused them not to be able compete. so, unless you call "law" a technology I don't include it in my definition. And since most of the other on demand companies are failing it leads me to believe it's not about technology or even strategy(unless you call breaking the law a strategy). Is my way the only way to look at it obviously not. Just like facebook didn't disrupt anything. they just executed better.
What you described is a "symptom", not a "definition". However let's say that you're correct and think for a second. Where do you pull out this notion that something has to be a technology to be disruptive? Here's the real definition of disruptive: http://www.merriam-webster.com/dictionary/disrupt There were many cases in history where people came up with disruptive invention, philosophy, business model, or any idea. Anything is disruptive if it renders the previous approach obsolete. Napster was disruptive, but both illegal and a failure. Based on your definition Napster is not at all disruptive. What else would you call it then? Being disruptive is not just about a small number of successful case studies mentioned in Christensen books.