Toggling toolbars leads to reduced anonymity.

If you visit panopticlick.eff.org from the TBB, you're roughly in an anonymity set of 1 in every 4000 users. Now turn off a toolbar in View>Toolbars and your fingerprint is unique or 1 in a million or so. Subsequent restarts of TBB do not toggle the toolbar back to default setting.

I suggest making toggling menu / navigation bars impossible in the TBB.

A scenario where this matters is a case when a user finds their anonymity compromised by accidentally toggling the menu bar off (like I did).

Trac:
Username: malaparte