Ask HN:How much harm can my data in wrong hand can do to me?

For e.g. Facebook know quite a lot about me. The worst case I can think of is lots of people spamming me to sell their product. so fundamentally If I am strong enough to ignore advertise, that concern may be invalid, right ? ( there are some people who want to watch the world burn. What they can do with my facebook's data. They do not have facebook's data. Do they ? ) What about google? I do not think they ever misused my data. If they want to misused it somehow, what are their option without legal penalties ?