Oh, that explains it! Explains why I don't share the bias, too, because I use my LJ friends list as my RSS aggregator. While I've technically got my various topics segregated by type, in practice I read them in one massive list: friends, interesting internet strangers, librarianship blogs, technology blogs, news, my library card updates... So I don't see it as a non-professional list, I see it as a generic list of news items updated on a regular basis.

It's not just you, though. Just today, I came across yet another person who keeps professional elsewhere and personal on LJ. There are readers of this blog who do that. I wonder if it's the same for everyone.