“Transport shaming” (sometimes called “stranger shaming”) is a term for gossip in social media about others' public behavior on urban mass transit. Using hashtags and tumblr, individual users post pictures of fellow passengers on public transport doing things that annoy them, holding them up for more or less anonymous mockery. Several major world cities have developed this custom, including London, Sydney and Singapore, but in each case the form of mockery was different, and raises interesting questions about how different cultures think about public behavior, how they use technology to regulate, or at least gossip about, that behavior, and whether or not technology changes the nature of social interactions.
In 2014, riders of Sydney's metro, called CityRail, spontaneously created the Twitter hashtag thread #cityfail to post images of bad rider behavior on trains and buses. (It had previously been used over 2013 and 2014 to post complaints about crowds and delays.)
Metro.co.uk: http://metro.co.uk/2014/10/20/have-you-been-transport-shamed-4913614/
In previous years, riders in London have posted images and stories of other kinds of bad behavior such as groping. When one man created a blog entitled “Women who eat on the Tube,” to ridicule women on the London Underground for their appearance, women staged a flash mob protest, “Women who eat wherever the f**k they want,” taking to the trains with food (and T-shirts bearing their slogan) to take selfies for the Internet.
National Post (2014): http://news.nationalpost.com/2014/04/14/women-who-eat-on-the-tube-londoners-lambaste-artist-for-posting-stranger-shaming-photos-online/
Indeed many people have considered surreptitiously-taken images as another kind of sexual harrassment, like groping. In London, police created an anonymous online tip line so that riders could report people who were taking pictures of other passengers without their consent.
Londonist: http://londonist.com/2014/04/public-transport-and-the-rise-of-stranger-shaming.php
In Singapore, the Straits Times social blog STOMP (Straits Times Online Media Presence) solicited transport shaming images from readers. Many submitted the typical images of feet on seats and messy eaters, but others submitted images of non-Chinese or “mainland Chinese” riders to ridicule them on racial grounds. For instance, a STOMP reader submitted a photo of “foreign workers” asleep on a train platform. Comments centered on people's opposition to immigration.