Wow
Hah, I didn't know people still used livejournal!
LiveJournal's security team has disabled some media features on the blogging site after a quick-spreading worm stole user email addresses and caused entries designated as private to be available to everyone. The self-propagating exploit spread to users who were logged in and did nothing more than view a LiveJournal posting …
Embeds for all domains but the offending one are re-enabled as of yesterday sometime, after the patch fixing it was pushed live.
http://community.livejournal.com/lj_releases/49901.html
I'm betting the 100 accounts number was an early guess; I'd guess 500-3000, based on the number of news post comments and how very easy it was to spread.
I missed getting hit by it because I didn't think to bring my laptop with me when I went out that night; by the time I was back, it was blocked.