The other day, I was talking to the CEO of a leading international hotel brand, and as is often the case, we got onto the topic of Airbnb. And he admitted to me that he was perplexed by their success. He was perplexed at how a company that depends on the willingness of strangers to trust one another could work so well across 191 countries. So I said to him that I had a confession to make, and he looked at me a bit strangely, and I said — and I'm sure many of you do this as well — I don't always bother to hang my towels up when I'm finished in the hotel, but I would never do this as a guest on Airbnb. And the reason why I would never do this as a guest on Airbnb is because guests know that they'll be rated by hosts, and that those ratings are likely to impact their ability to transact in the future. It's a simple illustration of how online trust will change our behaviors in the real world, make us more accountable in ways we cannot yet even imagine.