As a wise man once taught me in a public choice class, excludability depends on the state of technology. Example:1 the Pay & Sit park bench.
Design student Fabian Brunsing has devised a fiendish device that makes pay toilets seem positively munificent: Dubbed “Pay & Sit: The Private Bench,” it consists of a bench covered with retractable metal spikes and a coin slot. If you want to sit down on the bench without an array of spikes jamming you in the keister, you’ve got to pay €0.50 (about 70 cents US).
As seen below, this causes the spikes to retract so you can sit on the bench, and also activates a timer. Shortly before the timer expires, you’re warned by a buzzer to get up; then, the spikes shoot back up. Beware!
Spikes, it seems, provide strong incentives.
Hat tip: Anthony Martin.
Filed under: economics, video | Tagged: economics, public goods |
Brad Taylor's Blog 
Hmmm, pretty sure this is gonna be abused by someone with a spike fetish.
I’m pretty sure criminals will pay the fee, duct tape a victim on the bench, and leave. What an effective way to drive the law abiding public away from a park.
hmm .. interesting, so if somebody inserts the coin 2 -3 people can sit?
[…] to capture the gains from trade. Excludability depends on technology; but since technology changes, new exclusion mechanisms can arise, meaning that the publicness of a good is not a fixed […]
Necessity becomes will. – Italian Proverb