Location-efficiency is "a measure of the transportation costs in a given area," and it includes not just car ownership, but also if the area has reasonable public transportation. Basically, if an area is a "compact" neighborhood with good bus or rail service – and so having a car is not required – then the corresponding foreclosure rate was probably lower. One possibility is that the money saved by not owning your own car (more details here) can mean more money to spend on housing. As Autopia points out, there could be a lot of other reasons for this connection as well, but for the car-sharing crowd, this is another reason to think about staying away from owning a vehicle when other transportation options are available.
[Source: Autopia | Image: taberandrew - C.C. License 2.0]