Enrico Zini tips how to put /etc under subversion control. As one of the follow-ups mentions then you can mirror the svk repository into a regular subversion server to then have /etc/ remotely backed up. I'm not sure how it would be best structured, but it should be feasible to also use it to have shared configuration files across multiple servers (all pulling from the same subversion repository).
# Install svk
apt-get install svk
# Initialize a depot in /root/.svk
svk depotmap --init
# Import /etc making it a working copy
svk import --to-checkout //etc /etc
# Make your depot not that readable
chmod -R go-rwx ~/.svk
# Remove volatile files from revision control
cd /etc
svk rm -K adjtime ld.so.cache
...and voilà, you have /etc/ under revision control, without CVS or .svn
or {arch} files around. The syntax of svk is just like the syntax of
svn, of which it's a distributed extension.(via email from Robert Spier)
