While there is an option to mark individual bookmarks as private, it is easy to occasionally forget to mark a bookmark as such. Additionally, private bookmarks show up in searches on the user's local computer which may be undesirable in some situations. Some possible ways to fix this might be:
- allow users to mark an entire tag as private and hide bookmarks associated with it
- allow the default option to be to mark bookmarks as private if the user chooses
- allow a user to still use the service and share bookmarks, but not have the bookmarks associated with his/her id
- disable searching of private bookmarks through the plug-in interface when an option is selected

I'd be wary of calling any feature development as "shouldn't be too difficult to develop" from a presumably non-programmer point of view, but I agree that more robust privacy features are sorely needed, such as privacy toggling not only for single bookmarks, but also for tag bundles, default bookmarking and for network members. If delicious would have more finely grained privacy settings, delicious would be *the* invaluable tool for any researcher and power user.

Thanks for all the suggestions! We take privacy seriously, and we work on establishing a good balance between this need and our focus on social (public) bookmarking. It's helpful to hear recommendations for adjusting this balance.

aetherane:
"allow users to mark an entire tag as private and hide bookmarks associated with it" - There's a long discussion about this in another thread: http://support.delicious.com/forum/comments.php?DiscussionID=1103

"allow the default option to be to mark bookmarks as private if the user chooses" - We know people want this, but Delicious is primarily about shared bookmarks, so it's a tricky thing to consider.

"allow a user to still use the service and share bookmarks, but not have the bookmarks associated with his/her id" - Can you explain a little more? I'm not sure how this would work in practice.

"disable searching of private bookmarks through the plug-in interface when an option is selected" - This is interesting. How would it be useful to you?

cplamper:
"privacy toggling not only for single bookmarks, but also for tag bundles, default bookmarking and for network members" - Hmm, would you want the privacy toggling for tag bundles to hide the bookmarks inside the bundle, the tags inside the bundle, and/or the bundle name itself? I haven't thought about privacy toggling for individual network members before, but I see how it could be useful.

bdinesh:
"option to prohibit private bookmarks while doing synchronization to PC from plug-in" - I've heard this suggestion before from people who want to use their Delicious bookmarks at work, but without their personal (private) bookmarks transferred onto their work computer. Is this what you also have in mind?