Pay-Per-Use Electricity in Public Spaces

In my recent talk at LIFT, I used a photo of electrical outlets in public spaces denying their public use to highlight the issues around the ownership of the infrastructure providing ubiquitous experiences. I wanted to suggest that it does not mean that the infrastructure is out for us to profit from it. In other words, access has often a cost (financial, proper devices, privacy, time, …). In the meantime I spotted this beautiful transparent box at the Espacio Movistar that prevent people to get access to plug their electric devices unless that have a key. It reminds me of some fast food restaurants in Switzerland in which customers need to ask for the key or codepass at the counter to get access to the restrooms.

To further exemplify my thoughts, it seems that the increase of mobile devices in need for power has become a problem and a business opportunity in some airports.

Does the Dallas/Forth-Worth airpot set the standard by now providing pay-per-use electricity?
Relation to my thesis: the constraints to seamlessness