As someone mentionned, there is no privacy on del.icio.us per definition. Everybody can see everybody else’s links. All of them.
On a whim I fully switched to del.icio.us and now that I have started using it ‘for real’ it looks really nice. Furl is much slower and tags are way cooler than categories. You can surf del.icio.us easily where as in furl you would have to click and click and click until you get to a cool page.
The point is I was never really using furl’s killer feature namely the one that they store all the pages you ‘furl’ which also makes it much easier for them to analyze the content you have given them to exploit.
Whatever the privacy issues with furl: now that I tried both services, I enjoy the quick and simple delicious tagging instead of the slow furling.