The social proof that a couch surfing reference brought was second to none. Each one boils down to this "I, a stranger, stayed for a few nights in this other strangers home for free, and they were good human beings". That social proof carried to any part of the globe you visited. I cannot think of an internet app that brought people together in a more meaningful and wholesome way at scale. It was great while it laste…
This was also the success secret of the early church. The apostles and shepherds who visited believers in other cities brought with them such social proof in the form of a written letter.
That was very standard in the Roman empire at the time. Formalized patronage relationships were one of the core social organizing principles and given the distances, a letter from your patron to one of their contacts was _the_ mechanism for social proof.