Some thoughts:
- Have you thought about some type of timeline view with a clickable element that has a size dependent on the number of bookmarks for the day? When you click on that day it displays the sites you bookmarked on that day along with the top 2-3 words from each site in some type of auto-sorting word cloud?
- On the flip side, what if you had a word cloud generated from all of your bookmarks where if you click on a specific word, it shows your interest in that topic over time?
- Looking forward in time, what if the plugin could make recommendations for sites you might want to visit in the future based on the sites that you have already bookmarked? Sort of like a personalized Digg whose recommendations would change based on what you bookmarked in the last 30 days?
- Along similar lines is there a way to comb through the browser history and spot specific pages that have been visited multiple times in the past and recommend to the user that they be bookmarked to save a search engine visit, etc?
- It seems like the plugin is checking to see if the bookmark is live. Any possibility that in case of linkrot that it could suggest the bookmark be edited to point to one of the various archive sites out there that has a live snapshot of the site?