The site been blacklisted by Twitter, Facebook, and major email providers as malicious/spam. Over the last week, nobody has been able to post the website on social networks, or send any emails with their URL. Lyon has posted a summary of the relevant details on Reddit in the hope of obtaining useful feedback regarding what the cause might be. However, none of the answers there right now seem particularly useful, so I'm hoping the slashdot community can help him out by posting here.
Lyon indicates that the blackout has occurred at a particularly crucial point in the campaign to kill the TPP, as most members of the House of Representatives would likely vote against it were it brought to a vote now, and as pro-TPP interests have started to escalate their lobbying efforts on the House to counteract what would otherwise be a no vote.