According to a new study conducted by the French analytics group Semiocast, Pinterest has reached 70 million registered users. The findings were conducted using statistical sampling and by crawling Pinners' public profiles.
The report was also able to determine that 20 million of those users pinned, repinned or liked a pin in June 2013. Semiocast also found that 79% of those active users are based in the U.S. (The researchers determined geographical information by compiling users' declared location.)
When I reached out to verify the report, Pinterest's Head of Communications told me that they don't disclose internal numbers.
However, he did suggest that a February 2013 Business Insider post reporting 25 million registered Pinners was quoting a third-party number for users located in the U.S. and referred me to a Reuters article from the same month citing digital analytics giant comScore, which reported 48.7 million unique monthly visitors worldwide.
A full summary of Semiocast's findings is available for viewing here.