NOTES:
Here's another simple premise: Teleportation - it's not very likely but what if it were possible?
What are the implications? Some are obvious (no airplanes or cars except for fun), some are less so.
A velocity damper is needed to absorb the potential energy difference that is produced when you teleport from a mountain to a valley and the velocity difference that occurs when you teleport from Canada to Florida (different tangential velocities due to different latitudes) or New York to LA (a vertical velocity due to the rotation of the earth).
A flash crowd is a crowd that appears whenever and wherever something interesting is happening. If we assume that teleportation is cheap and easy, a crowd can grow very quickly, since it draws on the whole world's population of possibly interested parties. We see some similar effects with popular web sites - "teleporting" to a web site is easy, so an overwhelming number of hits can happen to any site that is attractive (see the Risks forum for a mention of this http://catless.ncl.ac.uk/Risks/17.86.shtml#subj8 )