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I get the exact same question, I say where does company shares come from. Also how much money is Facebook worth? That worth is now shared with the users. It usually makes them rethink.
If people see more commercial and promotions I'm sure they will be more open to it. Also sadly thanks to all the scams people are generally very close minded and I can understand it. The best thing is to not start work the money part or they just ignore what else you say after wards.
Ps. I made a friend invest yesterday :)