+ Delicious is lagging behind in mobile support.
+ Delicious could be taking more advantage of the conversation that people are having in their Notes section.
+ Delicious could be taking advantage of the links that are shared between users: help me find users that have similar but unique interests as I do. This would be true social networking on Delicious!
+ Delicious places priority on what is "Hot". This is not terribly useful since a lot of "Hot" links have already made the rounds on Twitter or in my Google Reader first.
+ Delicious could be taking advantage of links that are not yet popular but have a strong interest in category niches.
+ Delicious could be taking advantage of a user's top 10 tags: it's not an accurate assessment of a user's interest, but it gives me a quick assessment if I want to subscribe to their feed.
(I wish I could make another Delicious, but I'm not a programmer!)
Even if they aren't capable of evolving it, I wish Yahoo would at least make it fast enough that I don't cringe every time I use it.
It feels like Delicious could have been the start of something even larger than a bookmark service, it's my primary resource for finding specific content (eg: rails + tutorial, photo + howto, etc.) I'm aware that that is a fairly large technical barrier in terms of how search works, but I feel it proves the potential for something really, really awesome. A real social search engine if you like.
Ever thought about buying it back off Yahoo?