> What other laws of physics have changed since I was in school?

Sorry for the late reply -- I'm traveling. What I said in my original post is quite uncontroversial. When charging a capacitor one must not think in terms of voltage (which is an effect, not a cause of charging) but of current.

> The important factor for charging time is how many joules/second you can stuff in, not how much current (coulombs/second) is flowing.

You're confusing cause and effect. Capacitor charging is accomplished with current -- voltage is an effect, not a cause.

The voltage on a capacitor is the time integral of past applied currents. Want to change the charge level on a capacitor? Apply a current and let the voltage change in response.

> You can pull a helluva lot more joules/second out of a wall outlet than you can a micro-USB connector.

Non sequitur, the issue is how much current the capacitor can tolerate. And attaching a capacitor to a wall outlet will not work for multiple reasons.

The ideal charging source for a capacitor is a constant-current supply set to provide a high, but not damaging, level of current, then when the capacitor's voltage limit is approached, shut down the current supply.

The worst possible source for a capacitor is a constant voltage with substantial power available, which will destroy the device.

As I originally said, "Capacitors aren't charged by voltage, they're charged by current." Concise, and quite accurate.