In case you don’t follow web, tech, and social news sites, there’s a vocal minority that claims that Twitter is the next best thing since sliced bread.

One of the arguments of pro-Twitter bloggers is that Twitter is quickly becoming one of their top traffic referrers based on their web logs. A particularly noteworthy graph is from Calacanis who describes that Twitter has sent ~45,000 people to his startup (Mahalo) in the past 6 months.

That’s an impressive number, of course, and helps drive interested entrepreneurs and bloggers to start their own twitter accounts to try to recreate this effect. And before I get to my point, Twitter is certainly a great self promotional tool, and I think it’s a great tool to interact with your peers and others interested in you and your business. However… that being said, there’s some fine print to these statistics.

The way Twitter works is that people “follow” you to see your updates. So you tell your friends, your fans, your customers to “follow” you on twitter. It’s kinda like a private RSS feed for them. They see updates from you and anyone else they follow. (me on twitter)

So, of course, if you link to your site, people who follow you might click through. That’s great… but it’s a closed pool of people. A closed pool of people who already know who you are and were interested enough to “Follow” you on Twitter.

So, how many of those ~45,000 visitors to Mahalo were actually unique individuals? No more than 21,000 (or whatever number of followers Calacanis had at the time). And these are people who already have an active interest in Calacanis. Realistically the 45,000 may represent only 4000 distinct people clicking on multiple links over those 6 months. In many ways, you are preaching to the choir. And while there is value in that, perhaps not as much as the raw numbers would lead you to believe.

As a comparison, I think there’s more (different?) value in 45,000 visitors from Google or scattered across multiple other sites, as those possibly represent “fresh” visitors.

That being said, I think Calacanis is doing it right, in that he’s driving traffic to his startup rather than his blog (where he recruited his Followers). I think if you are simply trying to drive Twitter traffic back to your blog (or where ever you recruited your Followers), then you are simply driving the same people back to the site who would have gone their anyway (via Web or RSS). There’s no harm in that, but then the warm-fuzzy feeling you get from your Twitter referrals may be even more misleading.