Of all the social media platforms, Twitter is the one that puzzles marketers the most. The typical observation is that they don’t get it and can’t figure out why it’s important.

EMarketer shared some research recently from ExactTarget that provides an easy answer: Twitter gives you a way to reach people who have loud and active voices online. Once you’ve gotten their attention around your message, you’ve got a good chance that they will redistribute that message somewhere on the web.

How’s that work? ExactTarget shows that the 26 million monthly users of Twitter are three to five times more likely to comment on blogs, post to forums, participate in view sites and blog themselves than the average Internet user.

“Consumers active on Twitter are clearly the most influential online,” said Morgan Stewart, principal at ExactTarget’s research and education group, in a statement. “What happens on Twitter doesn’t stay on Twitter. While the number of active Twitter users is less than Facebook or email, the concentration of highly engaged and influential content creators is unrivaled—it’s become the gathering place for content creators whose influence spills over into every other corner of the internet.”

The conclusions suggest that the time spent investing in an audience on Twitter is likely to have an exponential impact. This is the crux of social media marketing, and provides a simple justification for using a service that at first seems fragmented and chaotic.