Some musing on stargates brings up some questions:
Will the builder of a stargate be able to charge a toll for its use? If not, how would they amortize the cost?
Will a stargate have a (digital) key, so only authorized users can use it? Will the owner have to have an armada patrolling to stop unauthorized use?
If I send a probe from Earth to Mars (or other pair of planets in the same system) will I be able to build a stargate between them? This could be very profitable for fast, easy trade if a use fee can be charged. Or is there a one stargate per system limit?