Just how big a part of the link economy is content sharing? According to a study which looked at behavior across some 300m who share content monthly using the ShareThis button, sharing now accounts for approximately 10% of all traffic on the internet.

And when it comes to the source of this sharing, one site stands out above all others: Facebook.

ShareThis’ data shows that the popular social network produces 38% of all sharing traffic, slightly more than bookmarking services and blogs, which account for 34% of sharing traffic.

Facebook handily beats out both Twitter and email, which each generate 17% of sharing referrals. For the first time ever, Facebook now accounts for more than half of all content shared, clicks and traffic notwithstanding.

Given the numbers, it’s going to be increasingly difficult for marketers to ignore sharing as a traffic source. As Rubinson Partners’ Joel Rubinson points out, “sharing is bigger than fans, friends, and followers…it accounts for nearly half of the referral traffic that search accounts for.” Because of this, it has the potential to make a big impact.

But as with most forms of marketing online, taking advantage of sharing requires a strategy.

Indeed, TechCrunch’s Erick Schonfeld notes that sharing isn’t as viral as it’s often made out to be. He explains:

Links are much less likely to be clicked beyond the initial set of people they are shared with. In other words, if you share a link directly with me and I know you, I will probably click on it. But if I then pass that link along to people once or twice removed from you, the chances they will click on the link falls dramatically.

And when it comes to sharing, 80% of people share only one category of links and more than 70% will only ever click on one category, whether that is business, politics, or entertainment. Facebook is especially strong when it comes to sharing entertainment and even shopping links, whereas email and Twitter seem to make some inroads when it comes to business or health.

The implication of this: marketers shouldn’t ignore content sharing, but they also shouldn’t pretend that it’s a magic source of traffic. That it most certainly isn’t.

Getting the most out of sharing requires a deep understanding of who your target audience is. After all, different kinds of content is more or less popular on different networks, so any content or seeding strategy needs to take this into account. Analytics play a role in determining which sources of referral traffic produce better conversions.

And when all else fails, investing in some share-worthy content (aka linkbait) might not hurt either, at least for the time being.