(I am not an expert, just a hobby self-hoster)

Think of how police obtain information about people. They usually do an investigation involving questioning and warrants to receive records and put together a case. They must obtain consent from someone or get a warrant from a judge to search records.

Or, they could just buy info from a data broker and obtain a massive amount of information about someone.

Imagine if every company has this info and can tie it in to your daily life. Google probably has your data location history and can see exactly what routes you've taken lately. They can use that information, with timestamps, to estimate your speed. What if they sold it to your car insurance company, who then uses it to raise your rates because you are labeled as a speeder?

What if your purchase history is sold to your health insurance provider and they raise your deductible because most of your food purchases are at unhealthy fast food joints?

Now, with AI being shoved into every nook and cranny in the tech we use, AI can quickly get a profile on you if it is fed your chat history. Even your own voice is not safe if it can be accessed by AI. This can be used to emulate you - Interests, chats, knowledge, sound. People could use this to steal your identity or access accounts.