Comment 2 for bug 508832

As far as I can see, upstart should have restarted dbus (there's "respawn" in the config).

Regarding the pid file, this cannot get removed if there's an unexpected crash.
Why wasn't dbus not starting before the file had been removed?

Well, "stop dbus" does not appear to stop dbus completely (the pid is gone, but 3 dbus-daemon processes still running).

I can confirm though, that with a file /var/run/dbus/pid in place (even if empty), dbus won't properly startup again, after having pkill'ed dbus-daemon, using "start dbus".
Removing the pid file made it start better, but the system is still borked, e.g. dbus-monitor cannot connect - that's another issue though probably (and maybe cannot get fixed at all).