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]