I can see the immediate advantage to having access to your own bookmarks, no matter which computer you are sitting at. Up until this point, if it was a work networked machine, I could just log into the network and create my own personal preferences -- bookmarks included. But that did mean that I had to re-create those bookmarks in more than one place. I knew about del.icio.us, but had never thought of it in that context.
I can see the research implications too, where if there is more than one person working on a project and they have a shared del.icio.us account, bookmarks to important/significant web-pages/online documents, etc. makes it easier to share and also not lose that reference, which often happens when good stuff is emailed (and you end up spending time searching your email when you try to remember which web-page or document it was.)
A colleague of mine uses del.icio.us extensively, and does follow shared links to discover new, interesting linkages
When we re-did our library web-page some time ago, our web-master inserted del.icio.us links all over the web-pages, specifically the resource-rich ones -- though when I looked just now, our main page does not have a del.icio.us link!