Judged by the worst seller

In Rehab City there was a residents' page where neighbours sold things to each other. A cot the children had outgrown. A sofa before a move. Home-made cakes on a Thursday.

It worked because everyone on it lived within a few streets. If the cot wobbled, you knew which building to walk to. The page carried a kind of borrowed trust, and that trust was the whole point of it.

Then the doors were left open. Anyone could join and anyone could post. Within a few months there were resellers passing off copies as originals, people from the other side of the city with numbers that never answered, and offers that wanted a deposit before a photo.

None of them broke a rule, because there were no rules to break. They simply took the trust the neighbours had built and spent it.

The residents did not leave in protest. They just stopped believing what they read there, which is worse.

This is the trade every shared space faces. Check too hard and nothing new gets in: the page becomes a club of twelve people selling the same sofa back and forth. Check nothing at all and the people who arrive fastest are the ones with the least to lose.

Most of us assume a space is defined by its best members, the honest seller with the good photos. It is not. It is measured by the worst one, because that is the experience people remember and repeat.

Opening the door brings attention. Choosing who comes through it keeps the trust. Attention looks like the prize for a while, but it is trust that is still standing at the end.