Its advocates seem to think it is like dangling a plumb bob off an overpass. It isn’t. If the whole structure could be extruded in space (which will be necessary, there’s no way to launch something that large, ironically or otherwise), there’s no way to deploy it. If it could be deployed, it would all wind up in one tangled mess, or tear itself apart. Don’t argue with me, argue with Kepler.
http://www.freerepublic.com/tag/spaceelevator/index
Without actually reading and learning many of the details, I instinctively think it’s a ridiculous idea.