Anyone who has traveled to Hong Kong knows how ubiquitous the Octopus Card is. Distributed by a company which is majority owned by the Hong Kong government, the cards are used to pay for everything from public transit to groceries, to Starbucks coffee. It’s an incredible payment solution that’s used by almost everyone in the city.

But as hundreds of thousands of people gather in the city center to protest against proposed regulations that residents view as tearing down the last protections against the authoritarian control of mainland China, those same citizens are viewing their Octopus cards in a different light.

There is usually never a line at the train ticketing machines. Judging from an overheard convo, it appears that people are reluctant to use their rechargeable Octopus cards for fear of leaving a paper trail of them having been present at the protest. pic.twitter.com/s1rsgSnCqL — Mary Hui (@maryhui) June 12, 2019

Protestors in Hong Kong are waiting in line to pay cash for a single-use card rather then use an Octopus card that’s tied to their bank accounts and identity. Their fear, as QZ journalist Mary Hui notes, is that the government will track their data and location.

Already, China’s security apparatus are leaning on citizens. In one instance they allegedly requested that the organizer of a large Telegram group open their phone and reveal their contacts.

Potential privacy concerns are a huge downside for cashless technology. While electronic payments can make things more convenient for the people that can afford it, it opens up new avenues for government or corporate surveillance and monitoring.

On the mainland, the Chinese government is already experimenting with social credit scoring that can affect a citizen’s access to everything from home and personal loans to public transportation.

Examples like this are another argument against the push for cashless systems.

Indeed, as some cities in the U.S. consider — or enact — bans on cashless stores, companies are shifting their policies on how to develop the technology. Philadelphia became the first city to ban cashless stores in March and the state of New Jersey quickly followed suit. Other cities considering the bans include New York, San Francisco and Chicago.

As nations like China and India push to go cashless, it’s worth noting that the ease of use promised by integrated electronic payment systems can be coupled with increasingly sophisticated forms of surveillance. Locking citizens in to a model where all financial transactions can be tracked — or are intrinsically linked — to a smartphone, may be great for governments, but it’s potentially terrible for democracy and its support for free speech and assembly.