Here's a funny thing that happened to me.

I have an out of work friend who I introduced to Medium. He can write, he's fun, he's interesting. I offered to give him $50 for his first year of membership. He was embarrassed, but I said "Hey, if you use my referral link, I'll get all of that back within three years, so just take it."

He did. And then he signed up but forgot to use my referral :)

I'm okay with that, but it is a another example of a big flaw.