One r4r success story could be about two people who met through r4r and started a business together. They had complementary skills and by networking via r4r, they were able to turn their ideas into a profitable venture.
Well, when it comes to fanfic, R&R typically means that the author wants you to read the story and then give a review. It's a way for them to get input on their writing and know how readers are responding to it.