Imagine for a moment that a restaurant is trying to convince you to make a reservation for lunch. You’ll be in a lovely and relaxing setting, they tell you. You’ll meet regulars who can’t get enough of the place. But unless you bring three other people, there will be a twist.

You will most likely have to share a table with one or more total strangers. They may be compatible with you or they may be a complete mismatch. If they have more experience eating at restaurants, you may get humiliated. They may take five minutes to...