The issues regarding an UberSky type setup is legislation or regulation is running behind the technology and is trying to playing catch-up. In US cities where laws are in place strictly regulating taxi cabs especially in heavily unionized towns like NY and SF etc, that view Uber as holding out for hire ( and argue they should be regulated) as opposed to a genuine ride share are fighting like hell to control (and tax) the service. Uber has stated that based largely on their financial resources they will continue operating as if they are allowed to and litigate any challenges. They have also publicly stated that this strategy will allow their service to become so widley utilized by the public who will then become so dependent on it that no politician will dare incurring the wrath of the voters by inhibiting or legislating against the service. Their strategy seems to be working for automobiles but when it comes to aviation they aren't fighting local city hall they are up against the FAA which is a whole different kettle of fish. I'm surprised for the limited amount of revenue attainable versus the risk they would even bother with starting a GA ride share business unless it's a toe in water test run before they go after the likes of Netjets, Options etc. An example of how Uber flaunt or outright ignore municipal codes, there is a city parking lot near me where Uber drivers gather, some who distribute restaurant food even repackaging and adding personalized touches like adding condiments for final deliver. If a restaurant ever tried to do that outside a licensed and inspected kitchen they would be closed down.
I personally use Uber cars, the service is so good, inexpensive, convenient and professional I actually regret buying my last car which gets little use and I may sell it and just use Uber exclusively, aircraft travel however is a different story.