The downsides Peter points out got me thinking about Leonardo acting as a delicious server.
The advantage of del.icio.us (the actual site, not the software or idea) is that it aggregates a lot in one place. But for more specialised categories, running a delicious-like service for your domain of interest isn't a bad idea and that's where Leonardo could come in.
I've previously suggested that trackbacks could be used for annotating resources and that categories could be viewed as resources that entries in that category track back to. Pinging delicious is really just like a trackback but the actor isn't necessarily the source and the target is a category/tag rather than another entry.
So a team could set up a Leonardo server (once the functionality I'm talking about has been implemented) and set up categories for the team. When they come across a resource of interest they use a delicious/trackback-like API to tell that Leonardo server about the resource.
Another interesting result is that you've essentially namespaced your tags. So "leonardo" on jtauber.com can mean the software without clashing with other senses the tag might be used for.
The original post was in the category: leonardo but I'm still in the process of migrating categories over.