You can fish out child molesters who are relaying their IP addresses all over the world.
If the person was so inclined they could find out pretty much anything about you. It's a lot of effort and in all honesty, it's easier just to walk up and punch them in the face.
Don't go blowing your load on AV and firewalls though. The people that could potentially rip apart your digital identity generally don't care that much about individuals. They tend to be busier with pissing governments off and making headlines.