Searching of missing persons, classmates, frauds, scams and debtors. These requests we also meet very often in our work. To find somebody we sometimes need only 2-3 days, but some searching can be 1-2 months long.
Illegal using of your trademark, company name and etc. Maybe you see the same goods and products as yours, but which more cheaper. Or you see your book, song which called another "author" name and breaks your author rights, competitor using your ideas in his business...