cool cool cool.
I found this to be a surprising result.
What the mechanism? Is it the haircut? The facial expression? The quality of the photo? Maybe. Do those count as "biases that they don't take into account?" Could be. Would it be interesting to learn what those "biases" are? Yes!
Let's say you created an arbitrary classification ("number of letters in street address" or "cosine of age in minutes") and an alorithm could predict that based on a photo alone. That would surely indicate that the classification wasn't arbitrary and there was something more interesting happening?
At the very least you'd want to dig deeper.
72% is much better than:
* random chance (50%)
* human accuracy (55%)
* 100-item personality questionnaire (66%)
Binary, yes. Meaningless, no. Having multi-dimensional information is better than binary information, but having binary information is better than no information (or guessing). Telling me the temperature, humidity, wind, cloud cover, and precipitation outside gives me more information than just telling me it is hot or cold outside. But knowing if it is hot or cold outside is still far better than not knowing anything. You can still make decisions and take actions based on limited information, which you could not do with no information.
It takes 33 bits to single out a human. 72% means a substantial fraction of a bit -- it's not much, but combine it with a few dozen other clues of similar magnitude and you're really getting somewhere.