Lately on del.icio.us I’ve noticed that I always set my bookmarks to ‘private’, even if really I could just leave them public. It’s an opt in thing, but since the bookmarks are for me and not for other people, I mark them ‘do not share’.
I would really prefer a setting that would make sharing links on del.icio.us opt-in, instead of opt-out. Del.icio.us has a pretty good API, maybe I should write a new bookmarklet that makes sharing opt-in.