Drive a shift register with one pin...

Someone should implement this on an Arduino. You probably need to add a cap to slow the process down to digitalWrite() speeds, but it should still work pretty well!

Interesing oncept. Could be handy in situations needing just a little external hardware.

Not so handy where there might be several shift registers sharing a common data line & clock, with unique output load lines, where parallel output update is needed.

I wonder - is shiftout interruptible? If so, that might lead to some glitches in the output.

What a hairy concept. I can't see that being to reliable over the long term or very reliable as it relies on the input capacitance of pins. This will change with different chip manufacturers.

I read it as onewould install an external resistor/cap to work with the timing of the source part.

Hmm, I guess it does show the internal capacitance.
I still think I'd exgternal, determined empirically to work with the shfitout, or more practically the SPI which should have fixed hardwre, timing and the particular logic family being used.