Twitter’s Wallflowers Get a Little Less Timid. But It’s Still a Service for Watchers, Not Talkers.

Twitter gets described as a conversation or a cocktail party, but it’s really more like a stage play. A few people do all the talking, and everyone else watches and listens.

But that’s changing, a bit, as the service grows.

Barracuda Labs, a security company that says it has surveyed 19 million Twitter accounts, reports that 73 percent of Twitter users have tweeted 10 or fewer times. And 34 percent of users have never tweeted at all.

That’s a lot of quiet users, but it’s less than before: Barracuda says those numbers are down from 79 percent and 37.1 percent, respectively, in June of last year.

Barracuda also notes that Twitter had a huge surge in growth from November 2008 through April 2009, when there was a rush of publicity about celebrities who tweet (Oprah Winfrey, Martha Stewart, Ashton Kutcher vs. CNN, etc.). The company claims that nearly half of all Twitter accounts were created in that period.

But even high-profile Twitterers don’t tweet that much. Most of the messaging on the service, Barracuda says, comes from users with about 1,000 followers (see chart below; click to enlarge).

All of this makes for fun data points to snack on. But for Twitter’s managers and investors, the usage numbers underscore a key question the company needs to resolve: Is it a communications utility a la Facebook or is it a media company?

The Twitter guys have resisted the second notion, but that’s sure what the company looks like from the outside–because it distributes content created by a small number of people for a large number of people.

If done right, that can still be a very good business, especially if you don’t have to pay anyone to create the content.

But a service with a largely passive user base also loses out on some opportunities. Twitter’s plan to ape Google’s (GOOG) search advertising, for instance, won’t be nearly so robust if most of its users aren’t making tweets and searching for them.