They've been slopping about for the past several months, and it looks like they've finally given up on it.
Really, how difficult is it to have a site and service that stores links and tags? Even at a high volume of data, in this day and age it should be trivial unless the money's not there to support it.
According to http://blog.delicious.com/ , they cancelled the premium service in January, attempted to monetize it again via sponsored links in RSS feeds in March, failed to revise the site successfully in March, then had "site problems", and finally said this month that they would be transitioning back to del.icio.us, but they seem to have been unable to do that either. Now the site's either down or stating that it has too much traffic. They've completely screwed the pooch.
Yeah, I made the mistake of continuing to collect links via the site while its been slowly getting more broken. Been too busy to write my own simple self-hosted version.
Now I realize — obvious in retrospect — that I should have simply jumped to Pinboard as soon as I had managed to export my bookmarks a few weeks ago. (Or years ago when Delicious got "sunset" for the first time, and Pinboard first came out and everyone else but me switched over…!)
it's been down for a few days, I hope it comes back, otherwise all my bookmarks are gone :(