I think (correct me if I'm wrong here) that if you have one or two houses with solar it is much easier for that power to be consumed by someone that is being fed power from the same transformer as you are.
This would seem like a much more manageable situation than if everyone had solar in your neighborhood and it has to start stepping up through the transformers looking for somewhere else to go.
Now if every neighborhood starts pushing power through the grid and all of these systems designed to put 10,000 amps one way go to shuffling around a few hundred amps from neighborhood to neighborhood.
Even if everyone had a radio link to the power company giving instant feedback of their generation, it would still be hard to keep voltage constant as clouds keep turning thousands of individual sources up and down.
With less and less power coming from the actual power company, who will be in charge of the grid? Imagine when we meet the break even point and power companies can shut off most of the day, who or what are all those thousands of separate Chinese inverters going to sync to?
In my imagination, I see waves of frequency, voltage and current fluctuations rippling uncontrollably around from transformer to transformer. Whole pulsating neighborhoods throbbing and blinking as these devices struggle to interoperate. A battle-royalle of cheap buggy firmwares fighting it to see who has the real 60 HZ... long after the power company automatically disconnected them.
Oh the voltage went up a little, I'll be a good little inverter and match it...
Oh hey the voltage went up a little, I'll be a good little inverter and match it.
That phase is kinda weird, good thing I can reshape it a little when I match it.
Wow my output just dropped 16 volts, Guess we need more juice quick, better step it up a notch!