Truecaller works by sharing the contact details of all users. So if you are stored in someone's phone as "Jane Smith" and they sign up to Truecaller, anyone else on Truecaller can see that info as well when they search your phone number.
Yes, that's the main benefit for us. I've already avoided several twats who've been saved as "Pushy and abrasive", "TW Twat in Birmingham", "Chats shit and never books", etc.
Can they see who knows you tho ? Can they see the persons number who has you stored in there phone if I'm making sense ?