my 2c on that list. 1): It's questionable whether or not Uber has a network effect that sustains it as a leader in any market. The taxi industry is catching up, and so is regulation, and I suspect that some markets will become very competitive. This is not a defendable monopoly.

2): Dropbox is under attack from free/cheaper equivalents but defending well. It is still the easiest to use and have an incumbency advantage, but has made a few too many missteps (photos) to be comfortable.

3): AirBnB is under attack from booking.com and the like, but is a pleasantly strong business for now.

4), 5) and 6) all are fashion (or nightclub) businesses where the crowds happen to be, and the more they try to monetise the more they upset the crowd. Crowds can leave at any time.

7) Square face competition from Apple Pay and the like for payments, and payments is where they make their money. Out of the USA payment systems are far more advanced.

8) Judgement day will come for Apple when they successively fail to launch things that have an edge on everyone else, and as with RIM the decline could be fast. For now they are well ahead but my own pick is that Huawei will become the giant to beat.

9) Google is fat and happy, but their core revenue base is advertising, and when crashes arrive advertising falls.

10) Microsoft is resurgent, and I believe on the early steps of a long term turnaround program. The switch to the cloud means we are less reliant on any particular OS but Microsoft Office is dominant for business.