I've never come across a public loo in Australia that has had the flush button or lever close to the floor. Most buttons or levers are set in the wall above the toilet or on top of the cistern (or are like the one pastrygoddess posted). A few older style toilets have chains that you reach up and pull. They all seem designed to be pushed by hand, not by foot.
This is the first time I've ever heard of anyone using their foot to flush.
If it was a pedal type arrangement, I can see why someone would do that. Otherwise, no. It's inconsiderate to other users and risks damaging the toilet.