Where they'll end up
> it's only a matter of time before we see these machines on all our streets
No, not all of our streets. In some of the back alleys. In pieces. A lot of missing pieces, too.
Without a human driver, a driverless taxi is defenseless against thieves. In such cases, the crime would be only auto theft, no charges involving physical violence against a human could be brought. So the police won't prioritize them.
A 'driverless' car with its owner sitting inside is another matter. But taxis will be fair [fare] game.