An yet, it just works, looks nice, is fast on old hardware, mounts everything out of the box, controls your audio from the volume icon and gets out of your way in general. 17.3 is one the best out of box experiences imo.
That said, no it should not excuse poor security.
GNOME and Unity also have that, probably KDE too.
Does Linux have a standard API for surfacing interactive icons and menus in the menu bar? An ICCCM extension, perhaps -- set some properties on the root window and cross you fingers? Or would you have to do it differently for every different Linux desktop environment or window manager that supported such a feature?
[1] https://developer.apple.com/library/mac/documentation/Cocoa/...
Exactly. Unity has libappindicator, KDE has Plasma, GNOME Shell also has its own plugin API and there's still the old tray API in Gtk+ and Qt.