Do users pay for any of those services you mentioned? This changes the dynamic completely by forcing the user to become engaged.
At the core AirBnB and Uber are selling commodities. They appear to be the lowest-cost producer because of their cost structure and scale. The price advantage alone is a high wall to scale.
Could another entrant come and improve the AirBnB or Uber experience 10x? Maybe. I wouldn't bet money on it though.
The textbook response would be a price war. Raise prices in uncompetitive cities and lower prices in at risk cities. This is one of the tools Standard Oil used to create its monopoly.
You just pointed out another barrier to entry for Uber and AirBnB. New entrants will probably have less selection and higher cost. This is fatal in a fundamentally commodity business. There will be no competitor to AirBnB or Uber for the foreseeable future.
The barriers to entry for any competitors are highly behavioral. Consumers are used to using (and implicitly trusting) AirBnB and Uber. Any new entrants would have to replicate that. This is part of the reason why Jet.com will never beat Amazon.
Only 6% percent of Valeant's revenue goes through Philidor. However, this raises HUGE questions about the legitimacy of the other 94% of Valeant's revenue streams. How many other arrangements like this does Valeant have. Is it conducting it's business on its other channels in an above board manner?
A huge portion of Valeants growth strategy comes from specialty pharmacies like Philidor. The integrity of the strategy has now been called into question by investors.
Valeant is especially pernicious case of credulous investors looking at a rising stock price and skipping their due diligence. There's a lot of amazing blog posts from John Hempton and others outlining the problems with their story.
The elephant in the room I don't hear people discussing is the impending spectre of deflation. If the labor supply diminishes what happens to aggregate demand? Judging from the example of Japan, demands implodes as fewer people buy goods and services because they aren't working! This deflates the currency and pushes the economy in recession.
Most of the developed world is sloughing off huge portions of its working populations. For example, Italy is set to halve its workforce in the next decade. There are huge economic, social, and political ramifications.
What is a problem is selling taxpayer subsidized water to large corporate farmers in the middle of desert so that they can raise surplus crops while in the middle of the drought.
Agriculture is fine. Subsidizing corporate behemoths in the Central Valley while wrecking our environment is not.
Great! A book I recommend to explain how thoroughly screwed up water policy in the West is Cadillac Desert by Marc Reisner. Water policy has been run largely as corporate welfare for large agricultural growers at the expense of taxpayers and the environment.