Lion still has the concept (as does iOS), except it's rendered effectively useless by the new Automatic Termination feature and the correspoding quick state res

Lion still has the concept (as does iOS), except it's rendered effectively useless by the new Automatic Termination feature and the correspoding quick state restore, which is very close to what iOS does. Also, Lion hides the 'open app' indicator by default for new installs, so beginner users have even fewer hints at the concept of quitting an app.