I think the statement "There is also a distinct lack of filling stations for natural gas and low incentive for gas-rich markets like the US to use it" says it all. Regardless of which fuel choice an automobile maker wants to gets behind, fuel distribution infrastructure and price (supply and demand) continue to be a large part of the bottom line.
As gas prices go up and consumers continue to demand refueling convenience, the next challenger to gasoline will emerge. Obviously human safetly will play a big part in the selection process, but one of the biggest decision criteria will also be ease of refueling and cost.
CNG has been used on indoor vehicles, like forklifts, for years, but performance under a wide number of operating conditions is not that critical to a forklift. It's safe to say that engineers would have to spend several years learning how to properly burn CNG in an automobile. More than anything else, I wonder about safety. Gasoline is only under pressure after the fuel pump, while CNG would be under pressure during storage and along the entire length of the fuel system. There are some advantages to CNG being a gas rather than a liquid, but the whole system being under pressure is a little disturbing.
I know Fiat is a staple in Europe and not so well known in the United States, that is until a year or so ago when they made a concerted effort to get dealerships here and up their advertising (any recall the J. Lo ads?).
There are quite a few fiats cruising around my area and I have to say, the cars are adorable. But as far as driving an alternative vehicle powered on propane gas (the same stuff that runs my BBQ), I'm not so keen. I get nervous sticking the tanks in my car to go get a refill, let alone using the fuel source to fill my car tank. I think the industry would have to spend some time and money educating people like myself to get over the fear of propane as being highly combustible.