People who live in fear of their government deserve a better government .... luckily history shows those governments fail

Does it?

History shows that all governments fail, but does it show that governments people live in fear of fail faster?

Is history still relevant? The creation of cameras, high speed communications, and computers fundamentally changes the question. The capabilities of citizens, governments, and bystanders have all changed. The capabilities are still rapidly changing, e.g. facial recognition, and drones.

I don’t know, China is still going very strong, and Russia doesn’t look like of collapsing anytime soon.

They didn't use their metro cards but did use their cellphones, as it can be seen in the pictures. The government can easily know that they were there, as they can be triangulated using the cellphone towers information.

Not using their cards is useless.

There are several factors. - They mainly fear prosecution after the protests and the travel card as a evidence of their presence. Cell tower triangulation fair worse in court. - Many people are also using burner cards which are easy to purchase in Hong Kong. - The protest was decentralized and was mainly organized with internet forums and instant messaging software. Not using a travel card is only a mild inconvenience.

Burner SIMs or burner phones + SIMs? As long a the government can link the IMEI to a person there's not much anonymity bought with a burner SIM. Using a burner transit card isn't nothing, but there's pretty good surveillance infrastructure in place already (e.g. the hospitals).

With one million people on the street, I don't know if that information is really useful in this case.

But then that reasoning could apply to the train cards.

Our train cards (Octopus card) are often linked to our bank accounts so that we can use the Automatic Add Value Service (AAVS). The only people travelling to Causeway Bay and from Admiralty at that time would be protestors so it would be fairly trivial to link protestors to individual identities using the cards.

It wouldn't be too hard triangulating the cell towers because we have a huge population density and, hence, cell towers attached to nearly every building. But I feel this data would be harder to get hold of and may catch the hundreds of thousands of "innocent" people who live in those buildings.

Using triangulation to track a single person is one thing. Using it to track a million would be incredibly tedious. Whereas getting a list of everyone who got off at specific stations in specific timeframes is likely a single SQL query.

You spot 4 people using their phones without any context or knowledge and say not using the card was "useless". Is there something I am missing?

Most people don't understand the incremental nature of privacy.

I don't mean that in a dismissive way: I think that's a seductive thought and the root of many crude, defeatist attitudes towards informational self-determination.

Metro station are typically underground as well. So even a very precise triangulation could place you logically in a building above ground.

Unless there are bluetooth beacons or cell repeaters underground.