Not really any info on what exactly happened or what dangers resulted from it. People may want to change their passwords, just in case. I did. I agree with the sentiment here: This is unacceptable from one of the most-visited Web sites in the world. I hope they explain how this happened and what they're doing about it.
itechreport seems to think this wasn't so bad and there is no need to change passwords, though earlier they were suggesting changing any passwords that were the same as your Twitter account.
And there’s no need to panic now or change your passwords. Twitter has confirmed the DNS records were “temporarily compromised” which means user data wasn’t touched and the “hackers” simply redirected users to their own website.
The Huffington Post article (huffingtonpost.com) about iOS apps that upload contacts in the clear & store them on their servers is pretty concerning. Where I grew up, this would have been considered totally inappropriate & scandalous.