Migrant shopping trolleys

An image from a growing collection of photographs of shopping trolleys encountered in various locations around the world. A daily sight in most cities, and sometimes in more isolated places. It would be interesting to know how and where they migrate, and how often. With electronic tags / tracking devices it would be possible to follow their progress as they move around the city. Somebody could presumably write an iPhone application that would do the trick!

I wonder what the economic consequence of shopping trolley migration actually is? One thing is for sure - the supermarket chains are not interested in allowing disappearing trolleys to eat into their profits, which means that the cost is presumably passed on to us, their customers. A further extrapolation of this thought  leads one to conclude that it is therefore us, the customers, who own this fleet of migrant shopping trolleys that is distributed throughout the cities of the world. Since this distributed ownership is extremely diffuse and impossible to formalize or co-ordinate, it follows that co-owners must all all have equal rights of access and shared responsibility for the fleet. So what should it be used for? A few simple suggestions for guidelines:

Fair Use:
1 - Homeless people who use the trolleys to transport their positions from place to place: this must be considered a priority, on the basis of need.
2 - Racing: an ecologically sound alternative to motor sport: races to be arranged along the lines of 2 man bob sleigh events, on the main streets of major cities, which would be closed to motor traffic.

Unfair use
1 - Drunken yuppies who fill  the trolleys with booze, use them as mobile bars, then abandon or even destroy the vehicle when the party is over: to be actively discouraged, with extreme prejudice, if necessary!
2 - Prototype submarines; it is blindingly obvious that this is never going to work, so submerging the trolleys can only be considered a useless and antisocial act.