I was browsing the Smashwords site and discovered what seems to be a bug!

Several times when I put the iPod down, the screen switched to landscape view, and the controls vanished! And it wouldn't return to portrait view. The only way out was to hit the Home button and relaunch Stanza.

IIRC, it occurred when I was viewing a description of a book. Unfortunately, it doesn't happen every time, which means trouble-shooting it will be difficult!