Thanks to Debian bug 407171, if you had
mod_proxy installed in apache2, and upgrade to etch, it'll also install
mod_disk_cache, which means your
/var partition is going to fill up quite quickly.
This happened to 2 CLUG servers.
I don't think this is the correct behaviour, and I'm even more suprised to see that it the appearance of the bug is documented in a bug-report.