Here’s Xeni Jardin on why they unpublished some old posts after a disagreement with the person who was the subject of those posts:

This is a directory of wonderful things. If we no longer think something is wonderful, we have every right to remove it from this directory.

I’m not sure what I think of that. It’s clearly trivially true. They could take the whole site down tomorrow if they wanted to. But is it ethical to selectively remove posts as they have?

I can certainly think of cases where I’d say yes. Without mentioning names, there was once a blogger who posted mainly about Web design, PHP development, and so forth. After a certain news making event, the focus of his blog changed to criticizing members of a certain religious group (and ethnicity), and he attracted a vociferous community of readers who post even more bigoted things in the comments. Had I written any posts praising this person before the subject of their blog changed, I would have unpublished them, and I would not apologize for doing so.

I have no idea what happened in this particular case, but I don’t think there’s any kind of absolutist argument against BoingBoing’s decision to unpublish.