Bookmarks today are usually static i.e. we save something we like once and done. But many times, bookmarks have a life, some could be temporary (e.g. craigslist apartment search link) which don't mean much after a certain time period etc. So my idea is that we should have a bookmark service that is fluid and dynamic.
1) EXPIRATION DATE: A bookmark will have a expiration date/timestamp which is user configurable. Say be default 180 days. A week before this expiration, users gets a notification that unless they want to keep this bookmark, it will be deleted/archived. This way, your clutter of bookmarks that are no longer needed is auto managed.
2) CONTEXT: When I bookmark something and come back to it few weeks/month later, I forget the context of why I bookmarked it. Sure, many times you know why because you did it of course. But tell me how many times you have looked at a Bookmark and went "Why did I bookmark this again". Context is important because lets say I came across a nice blog on "How to Add Google Analytics on your website", I might want to bookmark because I am thinking about using it for a specific webpage for my startup. Alternatively, I could bookmark the same page to share with someone who is looking to learn google analytics. Stuff like that. Again, context also helps with #1 because if I am just apartment hunting, i won't need those bookmarks after I find a place.
3) SYNCING: A bookmark should just not be locally available on my computer but synced with whichever device/system I am using.
4) TAGGING: Tag and categorize bookmarks using an easy interface. I hate the folder structure offered by browsers today.
4) SIMILAR BOOKMARKS: A potential social feature where once I bookmark a page, based on the tag/category, it shows me other similar pages/bookmarks done by users. Don't reveal any personal user info of course but it might be nice to see what others are bookmarking in similar categories.
May be some of this is overkill but these are my desired features for bookmarks.