Yes I think this is exactly what bothers me about it too. The fact that I use bookmarks and send links to others makes the information slightly skewed.

I also think, maybe I'm missing something. Maybe it's actually decent information to have. For instance, if you send a link with source=newsletter to somebody, it still is the newsletter that brought both of you to the site. You may not have visited otherwise. And your friend, probably even less so.

I don't know. I still don't like seeing it. It really does defeat the purpose of making your site have pretty links.