David Karp, a co-founder of Tumblr Inc., which grew 166 percent from May 2010 to May 2011 (Guy Calaf/BLOOMBERG)

According to the new report, American now spend one of every six minutes online using a social network, up from one of every 12 minutes in 2007.

The data also back up the fact that Facebook is the dominant player on the social networking scene, surpassing MySpace as the most popular social network in 2009 and continuing to grow. The site now reaches 73 percent of the U.S. population every month.

MySpace is still the second-most popular social networking site, with 34.9 million users per month, though user engagement has dropped 85 percent in the past year, the report said.

And who’s nipping at its heels? According to ComScore, there’s a race brewing between LinkedIn (which had 33.4 million visitors in May 2011), Twitter (27 million) and Tumblr (10.7 million). All three networks had their highest-ever traffic in May 2011.

Tumblr saw the fastest growth in the past year — 166 percent from May 2010 to May 2011 — leading the firm to say that it may be nearing “that critical mass threshold that propels it to more widespread adoption.”

What social networks, if any, do you use? And have you noticed your use increase over the past year?

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