So now the govt can hack into your car and crash it

What's the difference?

'Their work, funded by the Pentagon's research facility Darpa, has so far received a mixed reaction from the manufacturers themselves.'

http://www.bbc.co.uk/news/technology-23443215

I do not think they are amateurs.

I imagine in certain circumstances it is possible that a person does not use their car for several day.
But have no idea that it's being tampered with? Mmm, I'm not so sure about that.
I guess if the person was on vacation and had left their car at home it is possible, or it if it's a planted ca, such as a hire car that has been 'fixed'.
It seems very much low tech at the moment.
But, the possibilities are there, I guess.