Behaviour of middle clicks wrt tabs

[Alexander Larsson <alexl redhat com>]

We have a bug report with patch for implementing switch-to-new-tab when
opening it via middle click:

http://bugzilla.gnome.org/show_bug.cgi?id=552496

I'm not sure what kind of behaviour we want here. What was the rationale
for the current behaviour? I'm not sure myself which is best. I use the
current nautilus behaviour in firefox, but I don't use tabs in nautilus.
Opinions?

At the very least I think having this preference displayed in the prefs
UI seems overkill. Its just not that important and we're trying to keep
the preferences dialogs small.