Has any of you ever conducted an ambassador program for your product?

I did, in the early days of Uber (when we still had to explain what it is). It was also a time when in Switzerland the barrier was higher for people to start trusting an American app that asks for your credit card before you can even start using it. So we thought word-of-mouth through Ambassadors might work well. We found them through social media and email outreach, offered them an individual invite code to Uber and free credits (for free rides) for each sign up that came in with their code. Additionally we organised small events where they were always invited to and they actually really got to know our small city team. I really enjoyed that program. It helped us a lot, but wasn't a big game changer in terms of sign ups (I should probably have scaled it more). One unexpected result was that it helped me get intros to awesome people and I could close a lot of partnerships because of it.