Not an answer, but a summary of some research, because I'm looking, too...
Several Thule styles claim to mount on a ford focus hatchback, but it looks like the non-electric hatchbacks have perforated rear spoilers, which would presumably allow the straps to pass through (not an option for us, with a hole-less foil / spoiler). Mind you, they also claim to work with the mini cooper, which has a similar foil. In both cases, the biggest risk seems to be to the rear wiper, actually (easy to forget that it turns itself on when you back up, and have your forward wipers on). You could try clicking around on similarly shaped models of cars on etrailer.com, I guess.
I read that the European version of the 2013 focus electric has a retractable tow bar, so perhaps those might be able to use a tow hitch rack (but we can't), or maybe we can with an aftermarket mod--see the trailer hitch thread in this section.)
I'm sure Ford would be delighted to sell us roof racks, but those have got to be murder on the mileage.