Here is whats going in the background that you do not know. They have a file with your name on it. When you double click it, here are some of the info that can be shown about you:-
name , age, height, spouse , kids , contacts, phone number of contacts, browsing history, devices owned, yearly income, net worth, chat history with everyone, browsing history, when you make calls and who you call and how long you talked, storage of all photos and voice records (maybe even video calls), location history, where you are now, which links you clicked, your job, debt, politcal views, religeon...
etc
They might even be
recording you using your camera and microphone without you knowing. Most people do not know about this, they just downloading instagram and start posting away. Unlike Nelson rating where a small group of subjects probably signed a contract explaining everything to them and will be compensated financially for participating in the data collection.
Of course if you are ok with this, no problem, there was a girl on the internet that broadcasted her whole life 24/7 AFAIK even intimacy. As for most people, they would not like a camera hanging over their head broadcasting all their life to strangers.