SkyTran is an invention with an exceptionally well-worked-out plan, but no SkyTran system has been deployed yet. That puts it in the category of entrepreneurial proposals/opportunities. IMHO SkyTran is the BEST entrepreneurial idea in the world today. How do I support this extravagant claim?
What product do Americans (and increasingly more of the world) spend more of their income on than any other? I believe the automobile is at or near the top of that list. One study predicted that SkyTran could replace 40-60% of automobile travel in urban areas (and I believe that's too low.) That is one huge *market opportunity*.
If you study the extensive material at http://www.skytran.net and http://www.unimodal.com, you will probably agree that the inventor, Doug Malewicki and his company UniModal Inc. have done their homework. Google a bit more, and you'll see they have been pitching this to transit districts around the country for years; so they can no longer be considered an unknown quantity. The invention is also based on a new fundamental technology -- the powerful and cheap Inductrack non-superconducting magnetic levitation technique developed at Lawrence Livermore National Laboratories. These are all hallmarks of a first-class entrepreneurial idea.
However, from a business point of view, the big sticking point with it is this: until Unimodal can actually build a SkyTran system and start selling it, there's no payback for anything else -- the scores of add-on products and components it will need or enable -- that other technology companies and startups could reasonably produce. Therefore, at this point the only project that makes sense is to help them get over the hump to acceptance of the core system, which is far harder than the typical start-up proposal.
Plenty of marvelous technical ideas die on the vine, or wait decades for situations and/or personalities that push them over the hump to acceptance. Fleming's penicillin waited 12 years; Gerard K. O'Neill's free-space colonies and solar power satellites from lunar/asteroidal materials could have been built in the 1970's (see http://www.ssi.org/), but may be decades more or never.
Today, oil prices and terrorism/Mideast instability create motive. Mature electronics and controls industries provide the means. I think the SkyTran opportunity is on the cusp of acceptance.
Perhaps SkyTran would more readily find an initial installation as a dedicated private freight system. That's how railroads came about. A dedicated freight system simplifies or minimizes many of the technical hurdles versus a passenger system; speed, reliability, convenience and safety are less important, and the traffic loads are more predictable.
As a dedicated freight system SkyTran may be implemented on a different scale: you could imagine scaling the concept up to a containerized freight transport system, or down to a small package transport system. (What is the practical range of scales for this? I don't know.) At all scales, the essential advantage for SkyTran freight is that it's a packetized network that can automatically route cargo to varied destinations at low cost.
Train transport may have an advantage of lower cost due to the legacy rail infrastructure and similarly low-friction transport technology, but the destinations are few due to the large size needed for a rail yard. Plus, every train needs a crew, and there are the (I suspect) higher costs of railbed maintenance.