Earlier today, we described how the Facebook application Causes is enabling users to spread the word about Election Day to their friends by “donating” their Facebook status message. The movement has grown significantly throughout the day, and Joe Green, the President of Causes, just sent us the latest stats on the scale of the action. As of 3:30pm PT:

• 1.6 million people have “donated their status” on Facebook
• 4.7 million status messages in total have been posted

These numbers are significant for a couple of reasons:

1. This may be the largest online political rally in history, with over 1.6 million people producing simultaneous social pressure for millions more to get out and vote.

How did Causes do it?  According to Green,

Starting Thursday night, Facebook users could sign up for the “Election Rally” on Causes.  This involved people “donating” their Facebook Status to remind friends to vote.  They could choose to promote voting for John McCain, Barack Obama, anything they wanted to write in, or just getting out and voting.

Then, shortly after midnight last night, about 1 million people’s Facebook Statuses were simultaneously set with a unified message to remind their friends to vote today. This rippled across Facebook, blanketing user’s feeds with reminders from their friends to go vote. This kicked off the largest online rally in history.

2. It’s the most widespread and interesting use of the Facebook Status API we’ve seen yet.

Facebook Status is one of the most prominent means of self-expression on Facebook, featured at the top of the profile page and the top of the News Feed on the home page. However, no application has leveraged the power of the status update at scale to date.

Causes has demonstrated that Facebook’s Status can be used as a tool to coordinate collective action. Expect to see more uses of Facebook Status like Causes’ in the future.