The problem is usually shading, not so much the capacity of the wiring, though, if you try hard enough you can exceed the rating of the final stretch of wiring to the inverter (or the little pigtail in the inverter if you connect all of the strings at max voltage/amperage). Shading can really upset the current flow in a set of parallel/series connected panels and can cause local hotspots due to overcurrent. Usually inverters are pretty smart about this and they'll detect that you are pushing it further than is responsible and they will just switch off. I've purposefully triggered such conditions to ensure my installation is safe and I was pretty impressed with how utterly painless fault detection, isolation and recovery are in modern inverters. I also had an older one and there it definitely wasn't all that friendly, to the point that the whole thing had to be hard disconnected from the grid before it would work again.