I am very much an Uber fan, but if you are looking for drawbacks that passage expresses one potential problem. Pre-Uber, acquiring worker talent required lumpier investments on the part of the employer. You would hire a bunch of people, with the expectation of keeping them around for a while, and then train them to do a bunch of things. Some of them would work their way up the proverbial ladder, based on what you had taught them, many would not. But you would train and teach them quite a bit, if only because there was no alternative for getting things done.
In a “sharing economy,” a pre-trained worker is very often on call for a short stint, when needed. The employer thus has less need to invest in option value from the full-time work force and that means less training. The result is that more workers will have to teach and train themselves, whether for their current jobs or for a future job they might have later on.
I submit many people cannot train themselves very well, even when the pecuniary returns from such training are fairly strongly positive. The “at work social infrastructure” for that training is no longer there, and so many sharing economy workers will stay put at their ex ante levels of knowledge.

Tyler Cowen on the deficit of training in the sharing economy.

It's not just the sharing economy, though. The whole knowledge economy sector seems to put less into employee training. Is this different than in decades past? I've worked my whole career in this space, I have no basis for comparison to a bygone era.

The usual caveats about causation/correlation apply, but with employee tenures being so short in the knowledge economy, perhaps it's not surprising that employee training has diminished. The pace of change, the dynamic competition, the rapid growth, and the constant organizational reconfigurations are other factors that lower the return on investment to on-the-job training. Though it may be cheaper to groom someone from within, it's tempting for the leaders in tech to just poach talent from other companies, never has it been so easy to identify top people within other company walls (thanks to services like LinkedIn and the generally higher connectedness of tech employees in this networked age).

There are exceptions, of course, but it's best to head into tech assuming you'll need to invest heavily in self-training and be pleasantly surprised if things turn out differently. Most tech executives I know are stretched so thin that actively training others can't even find room on the bottom of the list.

When I speak to most younger students and recent grads, I advise them to think of their education as a lifelong endeavor and not something that ends when they palm their college diploma. Especially in technology, many people will likely acquire new skills multiple times in their career, a college degree serving just as the first notable signal that they're responsible learners.

The positive is that the internet and web have created a vast reservoir of free knowledge. The difficulty is making sense of it all. White collar job knowledge, especially in tech, is either trapped inside specific people or company's heads or it's out there but badly archived and organized.