Twitter is expanding rapidly: the site now hosts 50 million Tweets every day, or about 600 every second. Twitter announced its latest figures this week, and though it did not disclose how many users it has, it drew about 75 million unique visitors last month, PC World reports. The site's growth has been extraordinary: just 2 years ago, it had 300,000 Tweets a day. The new stats didn't factor in spam.
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