On Monday, I ordered lunch from the Japanese take-out I frequent. At the register, I realized that I’d forgotten my wallet back at my desk. Sheepishly, I offered to run back and get it, but the owner handed me my food, smiled, and told me not to worry, just pay next time I come in. This was smart on a number of levels: it was good customer service, and — given how often I come in — he was all-but-guaranteed payment within 24 hours (unwilling to to jeopardize my future access to chicken katsu or udon soup over a measly eight bucks, I was back within the hour). But he was only able to do this because he knew me well enough to trust me.

Trust, however, often takes some work to build and can be difficult between strangers (though our ability to so at all is among the things that distinguish humans from the rest of nature). Remember when eBay started, and the idea of sending some random schmuck your money in exchange for a promise that they’d send you an item — as-described and in a timely manner! — seemed crazy? Turns out that worked rather well, with those who attempted to game the system getting punished for it.

But it’s one thing to fork over money for a product and quite another to (potentially) put yourself at risk of physical harm. Only a few years ago, very few people were willing to let perfect strangers into their car, let alone their spare bedroom: too darn risky. But thanks to services like Uber and AirBNB, putting that kind of trust in someone from out of town whom neither you nor anyone else you know have ever met, and who you’re unlikely to ever see again, is now a perfectly rational, relatively safe thing to do.