Other backends?

Hello, everyone.

Has other backends for bbdb (other than its own file format) ever been
considered?

I am asking because I have been thinking about Emacs and CardDAV
synchronisation. There is a tool to do bi-directional sync with CardDAV
servers and vdir (vCard.vcf) storages, called vdirsyncer. There also is a
rudimentary vdir tool for Emacs called "vdirel" (available on Melpa). 

However, a "rudimentary tool" is not what I would really like to use in
Emacs, especially since everyone knows about bbdb.

What about a vdir backend? Does the idea sound like something possible?

--
Vladimir Nikishkin (MiEr, lockywolf)