I am sorry if this is filed in the wrong Product but I could not find the right one for xfce4-volumed. In any case, as has been documented in the downstream bug (https://bugs.launchpad.net/ubuntu/+source/xfce4-volumed/+bug/607474), xfce4-volumed seems to leak memory, or at least consume an awful lot of it in relation to the rather minimal task that it accomplishes. Why should such a simple tool need so much memory, other than it's leaking it?
This bug should be closed, it concerns some backend used by xfce4-volumed, only on Ubuntu with certain configs. No original reporters gave me enough information to identify the issue they were having. I suspect it's a GStreamer issue.
It was probably this bug, which has since been fixed upstream in gstreamer: https://bugzilla.gnome.org/show_bug.cgi?id=614545