Professional social networking site LinkedIn is driving more traffic than Twitter.com to TechCrunch, the site reports. Although the tech blog’s Twitter account has 1.7 million followers, Twitter.com has been passed by Facebook and now LinkedIn as top traffic referrers. There are a couple important caveats: Twitter.com referrals don’t include traffic from visitors using mobile or desktop Twitter apps, and much of the content on LinkedIn is directly imported from individual Twitter feeds. So Twitter is indirectly responsible for much of the direct traffic and LinkedIn referrals. Still, it shows LinkedIn as a significant sharing force, helped by the March launch of the LinkedIn Today news section, which highlights the most-shared content on the network.