This capability was present in ST1, but I can't find corresponding setting in ST2.
(I think) there's some variance between OSs as to the menu items, but that's where you'll find it.
On Linux it's under the View menu > Hide/Show Tabs. It's something similar in Windows. I don't know about OS X.
Wow indeed, thank you! Is there a way to do this with a plugin?
upd. Yes, there is: window.run_command("toggle_tabs"). Found this out with sublime.log_commands(True).