This article in Business Insider underscores something I’ve long suspected (and blogged about before): That Twitter, despite all the hype and sensationalism, isn’t quite as big as the boastful numbers that splash across headlines. For instance, the article notes that of Twitter’s claimed 175MM registered accounts, 56MM (approaching 1 in 3 users) are following zero other accounts. 90MM accounts (over half the total membership!) have zero followers.

The graph above is a nice counterpoint to what was published as Twitter’s ‘hockey stick growth‘ in 2009. The inverse hockey stick above should give everyone (especially those investors whose due diligence valued Twitter up in the billions of dollars!) a moment’s pause.

This finding synchs with a piece of research I saw a while back from Edison Research which stated that the United States had about 17MM ‘active’ Twitter users in 2010. (‘Active’ was defined as those survey participants answering ‘yes’ to the statement, “Do you currently ever use Twitter?” – which is a pretty generous question in my opinion.) Compound the above with the revelation that 22.5% of Twitter users post 90% of Tweets. Net, net, it seems that a very small niche of Twitter users are responsible for almost all of the activity that might be defined as ‘engagement’ with the service.

Now, If you’re trying to communicate with this niche group – which I suspect is largely comprised of brands, marketers, social media people, self-promoters and celebrities, then Twitter might be a great tool. For reaching any other target group – soccer moms, accountants, car aficionados, sports fans, etc. etc., its efficacy to reach significant numbers of these people is called into question by these findings.

Here are a few other interesting figures that support my belief that Twitter is a micro-niche community with minimal broad audience relevance (or participation). These items come from Sysmos’ Inside Twitter findings.

• 85.3% of users tweet less than once/day.
• 92.4% of users follow less than 100 people.
• 93.6% have less than 100 followers.

With about 14MM unemployed Americas today, there are slightly more ‘active’ Twitter users than there are people out of work. So, if you work in social media as I do – where we and all our friends and peers are part of the 1.5MM people who follow more than 500 people on Twitter – we might want some outside context to balance any industry-insider biases we might have.

I have an exercise for doing just that.

I recommend taking a walk down the street and looking around. Walk into grocery stores, restaurants, parks and coffee shops. Take in the sum of all the people you see. Then ask yourself how many of them you think are unemployed (fully unemployed, not temps, because temps aren’t counted in the U.S. unemployment stat either).

If you’re being honest with yourself you should be overwhelmed by the sense that the vast majority of the people you see on the street probably are employed. The minority that aren’t, those represent the equivalent of your ‘active’ Twitter users. You know, the people you have any real chance of reaching on Twitter. (And that is if you set aside the other issues like Dunbar’s number, attention span and the short life cycle of a tweet.)

Oh… and Twitter 175MM members is a global number, the U.S. unemployment is of course national. So we’re being generous with this exercise.

I found the exercise sobering and useful. Maybe you will too.