Twitter CEO Dick Costolo recently held a press conference at the company’s San Francisco headquarters. The event marked the first time that the privately-owned company disclosed the actual number of its active users.

According to Mr. Costolo, Twitter now boasts more than 100 million users who sign in at least once a month. That number comprises all: individual people, brands, television shows and popular blogs.

Without a doubt, this figure itself is very impressive.

But Mr. Costolo included something else with the disclosure, which should carry just as much weight: that 40% of those active users do not actually tweet – they just read what others have to say.

“Wait a minute,” you might be thinking. “If they’re not tweeting, then they’re just passive accounts. And what in the world are they good for?” Actually, they are worth quite a lot, as we are about to explain.

Cue sports analogy
The Philadelphia Phillies moved into their state-of-the art ballpark – Citizens Bank Park – back in 2004.

Last May, the Phillies were playing the Mets. Home-field advantage. Let us assume for our purposes that the stadium was sold out, its seating capacity being 43,651. And as per Major League Baseball rules, each team had nine players on the field.

The game was tied up, top of the ninth, two out. Suddenly the news of Osama bin Laden’s death spread like wildfire all across the stadium, thanks to instant text messaging and mobile Web access to social media – Twitter posts and Facebook status updates.

To be within the park in those moments was electrifying.

People got up on their feet almost at once. Chants of “U.S.A! U.S.A!” spontaneously broke out from fans of both teams, and began to thunder from the entire stadium as a single voice.

There is no question that everyone watching the game on television at this point a) had just heard the news, and b) got goose bumps watching, knowing what they knew. You can see the video here, and get your own feel for what it was like.

Let us try to put what happened in terms of social-media interactions:

Brands: Philadelphia Phillies and New York Mets
Influencers: 18
Audience: 43,651

Every single one of those 43,651 in attendance were there because of their affinity for one of the brands, and perhaps some the influencers – in this case, their favorite players.

Not one of them was himself an influencer – i.e., could not induce crowds to show up anywhere – but collectively, this passive audience was just as important as the select few for whose sake they were there that day.

Audience matters
Granted, it is not every day that your brand or organization will get a chance at such interaction with its customer base during a historic event.

But the takeaway from the above example is this: while influencers are the ones who can spark attention, potentially draw the crowds in and get your social-media messaging out, it is precisely the amorphous crowds they do draw in that has the largest potential to spread your message.

It is within the audience that the real marketing potential lies. So ignore your “passive audience” at your own peril.

Influence, strictly defined, is “the capacity or power of persons or things to be a compelling force on, or produce effects on, the actions, behavior, opinions, etc., of others.”

And since the core premise of social-media marketing is “interaction” and “engagement,” marketers too often become fixated on the most directly observable aspects of these.

Put simply, marketers fixate on the movers and shakers, the rock-star endorsers of your brand, whose activity you can monitor, whose likes, dislikes, and interests are well-known, and whose reach you can measure, or at least model on a chart – and end up like the proverbial cat that follows the finger with breathless attention, clueless as to the moon it is pointing at.

Influencers are only as good as their reach within the wider, semi-anonymous audience, and it is the latter that marketers need to eventually get to.

Know thy audience
Marketers today should value every single member of their online audience.

Those 40 percent who may not be inclined to explicitly share their thoughts with you and interact with your brand through your preferred channels are still visiting your Web site, reading your email marketing messages, clicking on your brand’s links and banners and, ultimately, giving you their business. Are they not?

Anything in the ballpark of 40 percent is sizable enough to be considered almost as important as a silent majority. So marketers had better consider these people very carefully.

To start with, it is good to get back to the basics: Who among your audience is actively online and using social media for direct customer service?

Who is publicly expressing strong sentiment, positive or negative, toward your brand?

Which segments of your audience engage with your content, and why? Or why not?

And, most importantly, who is following your brand on social platforms such as Twitter and Facebook?

Home runs are exciting, but …
To conclude, we’ll leave you with another little nugget from Twitter’s Mr. Costolo. He is excited about that 40 percent figure. Why?

Because, as Mr. Costolo said, “[it’s]…an indicator Twitter is becoming mainstream…. people who are active on Twitter, but don’t publish – yet.”

Yet is what you should take away from that quote. Because that is a lot of eyeballs. And that is a lot of purchasing power and potential.

Yes, your influencers and brand advocates will occasionally deliver a cracking, bases-loaded, bottom-of-the-ninth home run. But it is that filled stadium, tens of thousands of audience members, game after game, that at the end of the day bring in the big money.

Josh Mackey is general manager of product at PeekYou, New York-based search engine indexing the Web around people that focuses on social audience services. Reach him at [email protected].