You are using quite an old version of cgminer (3.1.1) here. As a heads up for any newbies reading this, this is the latest version that supports the -S parameter. More recent versions expect to communicate directly with the the USB driver, so the setup procedure is quite different. Perhaps you would like to update your tutorial with this information?
Thanks for your suggestion, and I just put a note about this in the original post. I'd be interested to see the command for running block erupters under linux for the most recent version 3.3.1. Adafruit did say there was a problem with this under Raspbian, but that might just be because they were trying to use -S tags.