Portals like those seen in Narbacular Drop, Prey, and the soon to be released Portal have far more uses than just personal transport. For starters if you have portal technology you have the potential for unlimited energy…

Well that is assuming that the amount of energy required to maintain a portal is negligible. In which case you could create your own hydro electric power plant by sticking a turbine in between two portals and just add water.
Thermal gradients are another obvious source of energy. One end of the portal near a hot region (sun?) and the other near a body of water. Although this then raises the question of whether all the air on earth would be blown out into space?

So lets assume that portals do in fact require a large amount of energy to create and maintain. Not only in an effort to respect the conservation of energy, but to avoid the anarchy that would result from personal portal devices. At least this way governments, large corporations, and billionaires would be the only people in control of them.

Sure the technology would be abused but just think; here we have the solution to world hunger, population overcrowding, public transportation, non-renewable resources, and space exploration. All because portals allow objects to be transported from one location to another instantly.

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A really good book featuring this technology is Pandora’s Star by Peter F Hamilton.