As a CG person I can only suggest that you re-design the website to something fresher & more attractive to the eye to attract new users, because to be honest i've visited diigo a few times before i decide to give it a try and that's because i thought it was left back in time with that "boring" design (no offense) & to be even more honest, i tried a few other websites for note-taking/bookmarking first, because they felt more "clean"
We released a new version yesterday with a whole new redesign. Please check it.
Amanda B. commented
I completely, absolutely agree! I've been hunting around for a bookmarking tool that really serves my needs, and the utility of Diigo is certainly the best. (Huzzah!) But as a very visual person, I find the slightly dull, slightly outdated appearance of the website to be a big turn-off. A fresher, less-cluttered design with cleaner font choices would make Diigo completely unstoppable.
Michael Caillet commented