I would be fine with this behaviour if it actually increased the physical capacity of my hard drive.
Thus you can either interpret this as a bug report or as a feature request.

REPOSITORY            TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
//scrubbed//          latest              b82c34c9b7a6        48 minutes ago      -2.147e+09 B
//scrubbed//          latest              82640edb0178        About an hour ago   -2.147e+09 B
//scrubbed//          latest              9fc9d6285e9d        About an hour ago   1.872 GB
debian                7.5                 06af7ad6cff1        3 months ago        85.18 MB

• The output of uname -a:

  Linux hca 3.16-3-amd64 #1 SMP Debian 3.16.5-1 (2014-10-10) x86_64 GNU/Linux
  

• The output of docker version:

  Client version: 1.3.0
  Client API version: 1.15
  Go version (client): go1.3.2
  Git commit (client): c78088f
  OS/Arch (client): linux/386
  Server version: 1.3.0
  Server API version: 1.15
  Go version (server): go1.3.2
  Git commit (server): c78088f
  

• The output of docker -D info:

  Containers: 27
  Images: 59
  Storage Driver: aufs
  Root Dir: /var/lib/docker/aufs
  Dirs: 113
  Execution Driver: native-0.2
  Kernel Version: 3.16.0-3-amd64
  Operating System: Debian GNU/Linux jessie/sid
  Debug mode (server): false
  Debug mode (client): true
  Fds: 11
  Goroutines: 15
  EventsListeners: 0
  Init SHA1: 109743bc4105d1b3eff1d8fc989a38a2f7c32f4b
  Init Path: /usr/lib/docker.io/dockerinit
  WARNING: No memory limit support
  WARNING: No swap limit support