A discussion in another thread made me think - just how widespread are transporters outside Starfleet? First of all, I don't think your ordinary Joe can get his hands on one. After all, potentially, they are an incredibly dangerous weapon. There would need to be some heavy restrictions and regulations regarding their usage. Obviously, the government and it's institutions use them. Starfleet, the police, medical services (could be extremely useful for paramedics and cops). I can see much of travel and transport being done by transporters, as well. I don't think they'd replace cars (flying, of course), those tube trains or just plain walking for short distances (though I vaguely remember one of the Siskos talking about beaming the furniture into their new house). However, talking about long distance transport, from city to city or continent to continent, I'd be very interested to see what transporters do to the existence of aircraft and water-borne ships. Are there any tankers in the future? And with all that transporting going around, would there be 'congestion' and signal-interference in the air? 'Traffic control'? Land-line connected transporters could be used, I guess (would give a new meaning to the term information highway ).