Twitter has announced its number of daily status updates or tweets has now passed 50 million, closing in on Facebook’s claimed 60 million.

Announced on its blog, Twitter describes the exponential growth of the service since it began:

“Folks were tweeting 5,000 times a day in 2007. By 2008, that number was 300,000, and by 2009 it had grown to 2.5 million per day. Tweets grew 1,400% last year to 35 million per day. Today, we are seeing 50 million tweets per day—that’s an average of 600 tweets per second.”

According to a report by RJ Metrics last month, while Twitter is adding accounts at the rate of 6.2 million per month, only 17 percent of these are active each month.