The built-in "back" button in salesforce1 does not work properly when viewing a custom visualforce page; instead it brings up the Publisher "+" icon.

Here's our clickpath; detailed image to follow:

1. In our case, we start with a mobile card.

2.  Tapping on the mobile card ignores any href within the card and reloads it fullscreen (this is arguably a bug - see this forum post).

3.  On that reloaded frame, the "back" arrow works fine.

4.  We then tap from the reloaded mobile card into a (custom visualforce) detail view of the desired object.

5.  It is on this page that the "back" arrow totally breaks down.  At first tap, it brings up the Publisher "+" icon.  At second tap, it jumps navigation back 3 steps.

Update 12/16/13:  partner support has recognized the bug & escalated to dev, case # 10009288.

Here's a walkthrough of the issue which is getting scaled mercilessly; click through for a readable version: