Here's a nasty little bash one-liner to determine how much space is being "wasted" but .svn/ or .git/ or .hg/ repos in your current directory:
du -k | sed -nE 's/^([0-9]*).*\.(svn|git|hg)$/\1/p' | awk '{s+=$1*1024} END {print s}' | awk '{ sum=$1 ; hum[1024**3]="Gb";hum[1024**2]="Mb";hum[1024]="Kb"; for (x=1024**3; x>=1024; x/=1024){ if (sum>=x) { printf "%.2f %s\n",sum/x,hum[x];break } }}'