They are creeping in that direction though. Delta purchased their own refinery in 2012:
http://www.reuters.com/article/us-delta-jetfuel-exclusive-id...
Given that, "there is a deep, liquid market for jet fuel," is having Emirates airline and Emirates National Oil Company under the same umbrella poor strategy?
You're also omitting the fact/point that the energy industry is evolving very quickly and that calls in to question the established markets. Energy over-supply in general creates opportunities for disruption and new business models.
Yes. The only reason it exists this way is because they're both owned by the corrupt government/monarchy of Dubai.
Keep in mind that under the same umbrella you also have everything from banks to a cement company to hotels to a mineral water company. This isn't a coherent business strategy, it's just what happens when a single family rules over an entire economy and basically owns everything.
You could equally argue that is exists that way because they need to deploy extremely large amounts of capital. So, an infrastructure company in a region that is going through phenomenal, albeit temporary growth, makes a lot of sense. Once that growth levels off they could transition to higher-tech endeavors.
"Vertical integration can make a lot of sense in weird markets where goods aren't fungible or there isn't a high quality market for trading. Electrical power is basically the opposite of this though. There is a very very large and very liquid market for pricing electrical power. I see no reason that SolarCity can't just be a supplier to this market while Tesla Owners would be consumers." Yes, but the point is that there is a reason to combine those two, if the long-term agenda is to create a next-generation energy company, as opposed to simply competing in their respective markets, which was a response to pfarnsworth's comments.
I do agree with the likelihood of certain shareholders being negatively affected. You are also probably right about the motivation being cashflow, but that is due to circumstances/timing rather than a lack of synergy.