Humans make the decisions, but they make them in advance. Machines are programmed to parse the feeds and trade based on their content. This has almost nothing to do with retail investing. It has to do with big players paying for the privilege to front-run the rest of the market.
The listed other usages consist of:
* Trading against a party who is legally required to publish their intent to trade in a security in advance.
* Detecting large orders in the market and trading against them.
* A financial advisor producing its own report and trading on that information before disclosing it to its clients.
