Google blacklisted bit.ly several days ago in a move that caught many publishers off guard. We started seeing spotty reports of del.icio.us being blacklisted over the weekend and it has now gone full-blown with all del.icio.us links apparently being blacklisted by Chrome as hosting malware.
Delicious has changed hands several times over the years and recently was re-sold earlier this year to Science Inc. They also rebranded several years ago to delicious.com which is not blacklisted, but there are likely a large number of legacy .us links out there. [Edit: Thanks Kelson]
Bit.ly has now been removed from Google’s Safe Browsing list which is the list that Google maintains of known malicious websites that engage in malware distribution and phishing. [Edit: Correction, we are still seeing bit.ly links being flagged by Google's GSB and Chrome] It’s also one of the data sources that Wordfence uses to scan your site’s files, posts and comment for malicious activity and infections.