I always assume a random metal box left unattended on the street in SF will be broken apart and turned in for scrap metal within about an hour. Technically the half life of such things varies but downtown it's about 5-10 minutes.
We got pretty interesting results leaving a random beaten up metal box crying for assistance on the streets of Oakland: Most people walked past and ignored it, some tried to steal it, but a few people were actually quite kind and helpful!
