I am kind of curious how over-current protection is achieved with these systems.
Don't get me wrong; I think the concept is good.
But the circuit breaker is sized to protect the wiring between it and the outlets/devices it supplies. If you're already close to the max current the breaker can supppy, then you add on a second current source (the panels inverter), you could feasibly supply+draw more current through that circuit than it was originally designed to carry.
For example: a regular 15a circuit + 5a worth of panels (600w); you could now draw 20a through wiring that's only designed/sized for 15a, before the breaker trips. More current creates more heat, this is a potential fire hazard.
On top of that; switching the breaker off/locking it out doesn't necessarily switch off all power being supplied to that circuit. If you're not aware of the solar system that's also supplying that circuit from another point (very unexpected under current norms) This could cause you to work on wiring that you expect to be unpowered when it's actually live (you should always check with a volt meter anyway, but still, unexpected hazards).
I would imagine much of this has been thought about; but I'm curious about the solutions (or about the reasoning why it's not considered an issue)