I support this. I made Instagram followers/friends because of also following/friending them back. But unlike Instagram, there is no good way to know if a person has friended you unless you friend them back and it says "Mutual Friend." I see this as a way for those people who have no real life friends in osu! to make friends in-game. 
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EDIT: For those people who don't like the idea of being spammed by notifications, I'm thinking there should be an able/disable option?

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EDIT: For those people who don't like the idea of being spammed by notifications, I'm thinking there should be an able/disable option?