Twitter Inc. may be having a great week, since both President Barack Obama and Microsoft founder Bill Gates have started Twittering , but a report released this week by HubSpot Inc. says the site's rate of growth in signing up new users started dropping dramatically last fall.

Twitter had grown very rapidly over the past couple of years but HubSpot , a Cambridge, Mass.-based Web analytics company, said in its latest "State of the Twittersphere" report that the growth rate dropped to 3.5% in October compared to 13% just seven months earlier.

The report did note, however, that a recent study of Twitter users found that they are becoming... well, better Twitterers.

More: http://pcworld.com/article/187542/

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