73% Of U.S. Adults Use Social Networks, Pinterest Passes Twitter In Popularity ...

The U.S. is edging ever closer to social media saturation, with the percentage of adults using multiple social networks to communicate with each other now at 73%, and - partly thanks to the rise of mobile apps - the number of people on multiple networks now at 42%, according to figures out today from the researchers at the Pew Research Center.

Facebook - the world's largest social network with 1.19 billion users - remains the most popular in the U.S. as well, with 71% of U.S. adults on it. In other words, nearly all adults on any social network at all are using Facebook. That's four percentage points up from last year's 67%, Pew notes.

Moving down the ranks, there is a lot more wiggle room for the next-biggest network. LinkedIn - site that bills itself as the 'professional' social network focused on networking, job hunting and professional information and news - is hanging on at the number-two social network, with 22% of U.S. adults using it - up 2% on last year. Close on its heels is Pinterest - which has vaulted over Twitter to number-three position with 21% usage.

Twitter - despite the different services that it has launched to increase engagement like Twitter Music other discovery services; and despite the increased attention around its IPO - has only grown by two percentage points to 18%. Hot on its heels is Instagram at 17%.

For these sites, which are constructed in large part around advertising-based business models, critical mass is crucial: you won't visit a site if no one else is using it.

More to come.