We kept it simple and spoke with them about not using names and having identifying details in their recordings. They've really enjoyed inventing their "podcast nicknames". We've got all kinds - BikerBoy186, Little Man, Nessie (as in the Loch Ness Monster), Sparkles, Chook, Smiles. And a sign they've gotten this very simple message from us - hubby reports he got in trouble for using their real names in his feedback comments on their wiki pages AND they've all changed the titles of their pages from their names to their nicknames.
I know this is no where near the complete induction to digital citizenship students need, but it's a step - and one that our school hasn't done before, so this is a small step, but an important one in moving towards starting conversations about cybersafety and self-protection on the internet.
Image by: publicenergy @ http://www.flickr.com/photos/75424716@N00/243387436