There are plenty of reasons to do research on someone. You might be looking for ancestors to fill out missing branches on your family tree. Maybe you just need to know if a potential romantic partner or a blind date is on the up-and-up. What about roommates and neighbors? And let's not forget about potential employees and co-workers.
With just a little info and an Internet connection, you can find out everything you need to know fairly easily. You don't necessarily have to pay a service fee either. You can dig it up yourself without having to make a phone call or wait in line.
I've found a helpful tool for finding almost any kind of public legal document in all 50 states and some foreign countries. It has guides to finding records including: property, criminal, court, birth, death, marriage, divorce records, licenses, deeds, mortgages, corporate records, business registration, and many others.