[gus_massa]

Here in Argentina ~1/5 of the cars use compressed natural gas (mostly methane) tanks at 200 bars, because it is cheaper than gasoline. I don't remember any horror story of a crash, and these cars are generally considered almost as safe as the usual cars. The main drawback is that the tank is very big and uses half of the back trunks.

More information: http://en.wikipedia.org/wiki/Compressed_natural_gas

[StavrosK]

We do the same in Greece, the tank is 50-60 liters (not sure if that volume is when the gas is at STP or compressed), though, and takes around the room of the spare. That's also where they put it.