A February 2010 Edison Research study of Twitter usage and demographics is making the rounds on several blogs, and some readers think they have found a problem for microblogging marketers: Twitter’s failure to convert awareness to usage.

However, that finding is not about brand awareness—unless the brand is Twitter itself. The site rose in popularity last year and got plenty of attention from the mainstream press. The result? Almost as many people have heard of Twitter as Facebook.

At the same time, relatively few people who have heard of Twitter actually use it. That “conversion rate” may be a problem for Twitter itself, though the service still boasts tens of millions of users (and counting), and keeps those users engaged over time.

But for marketers, there is plenty of data to support targeting Twitter. The Edison study itself found more than one-half of Twitter users followed a brand, compared with just 16% of other social network users. Small businesses have found Twitter effective for lead generation, and Twitter users are more likely than Facebook users to respond to brand recommendations from friends. There is also evidence from companies like IBM and Dell that Twitter promotion can make millions.

Skepticism is healthy, but perhaps the most experienced social media marketers are onto something and Twitter marketing is worthwhile.