Shoe Recognition less Invasive?

As opposed to facial recognition and analysis.  Taking images of shoes and deriving information from the images, without the same privacy implications.  In BBC Technology:

Tomorrow's cities: Are your shoes giving away data?    By Jane Wakefield

' ... "Online retailers gather all kinds of information about shoppers and physical stores also want to understand how people behave in a shop," he said.  But, he admits: "A lot of these technologies are kind of invasive."

Hoxton has come up with a novel way of measuring footfall - literally by filming people's shoes.
Sherlock Holmes-like, its system can deduce a remarkable amount of information such as age, gender and social class of shoppers from their footwear.

"We have cameras at about 50cm off the ground and it points down so it is less invasive than facial recognition," he explains.

It is surprisingly accurate. It spots the correct gender 80% of the time, better than some facial recognition technologies, according to Mr Mann.  ....  '