My internship on the Khan Academy iOS team 12 years ago
I went through a paid internship. In my case it was for a couple of reasons:
1) I was underqualified for the position that I applied for. So they offered the internship.
2) Since I did not have a lot of (work) experience I guess it was a gamble for them to employ me "just like that". So it could be seen also as an qualifications test maybe.
3) Visas are hard(ish) so not employing me made it, let's just say more legal. Paperworkswise I've been working as a freelancer for their branch in a different country.