I see the default behaviour of Delicious.com has changed to make links private by default. Fair enough but it would have been helpful to get a warning. I wanted to show Jane a site I bookmarked earlier today and was surprised to find it did not seem to have registered so I had to resort to searching to bring it up. Later, on my laptop, I found that the site was listed on my account and that is when I spotted the changed status of several recent entries.
I can remember hearing a talk several years ago by Josh Schachter, who set it up in the first place. This was in the days before it was bought by Yahoo! and I recall that the issue of private bookmarks came up. To the best of my recollection, Josh and his team heard the request and went so far as to introduce the option but they deliberately did not make it the default mode because one of the greatest values of the site was the ability to discover interesting things by looking at what else people had discovered around tags you might have used yourself.
I can appreciate that user interfaces change over time but it is a useful reminder, every time I come up with a bright idea for one of my sites, that while people can be attracted by novelty, they also value continuity and not having to constantly relearn the rules of how things work.