The number of profiles on LinkedIn has grown by 300% since 2008. And while Americans are far more aware of Twitter than they are of LinkedIn, ~8% have LinkedIn profiles, compared with 7% who say they are tweeters, according to Edison Research.

Edison data suggests that the majority of LinkedIn users do not use Twitter, so introducing 'Tweets' into the ambient awareness of LinkedIn's user base may in fact provide those users with subtle reinforcement of the potential benefits (business-related and otherwise) of sharing status updates with their extended network.

Source: http://bit.ly/aWQGZG