Twitter’s battle with spammers is well-documented, and not surprisingly, one of the tools that makes Twitter spam possible is the fake account.

While the exact number of fake accounts is hard to accurately estimate, there’s little doubt they exist, and most likely in big numbers.

Fake followers fit for a President

Just how big? Earlier this month, security firm Barracuda Networks released a study looking at the issue. The study revealed an ecosystem of vendors dealing in fake followers. On average, for $18 per day, these vendors can offer blocks of 1,000 fake followers. And they can do it at scale: according to Barracuda Networks, some of the vendors have armies of up to 150,000 fake Twitter accounts at their disposal.

Apparently you don’t have to look hard for evidence of these armies being put to use in the real-world. The firm, for instance, suggested that U.S. Presidential candidate Mitt Romney, overeager supporters or a savvy opponent trying to make him look bad may have engaged in the purchase of fake followers as his follower count jumped an amazing 17% in a single day last month.

Barack Obama apparently has a problem of his own: according to a tool run by London-based StatusPeople called Fake Follower Check, 70% of the Twitter users following the Twitter account of the current President of the United States may be fake. That would equate to more than 13m fake accounts.

Fake, or quiet: does it really matter?

So is there an epidemic of fake Twitter accounts that everyone invested in the Twitter ecosystem — businesses and brands included — should be concerned about? Not everyone is buying that notion.

BuzzFeed’s John Herrman points out that not every legitimate user participates on Twitter in the same way:

Twitter defines active accounts based on logins, not frequency of tweets (apps like StatusPeople’s can’t see logins). Twitter has just north of 140m “active” users that log in at least once a month. Of those 140m, about 40% only read tweets. Tweet-shy accounts, [Twitter spokesperson Carolyn Penner] said, “generally follow and engage with a lot of accounts” — a trait that StatusPeople’s tool takes as a sign of fakeness. Throw in the fact that many of the largest accounts are on the Suggested User List, which helps skew their bases toward read-only users, and Obama’s “70% fake” figure starts to make a lot more sense.

This raises an interesting question: if we make the reasonable assumption that a substantial number of Twitter accounts that might mistakenly be considered fake because the individuals behind them are consumers of content rather than producers of content, is there a meaningful difference between real and fake?

For brands convinced that Twitter is a one-to-one communications platform built around conversations, is a shy account any more useful than a fake account? And if shy users, which potentially make up the majority of Twitter users, are, as Twitter says, prolific followers of “a lot of accounts,” can brands really expect to stand out and reach them in meaningful ways?

The answers to these questions aren’t entirely clear, but brands investing time and money in their Twitter presences would do well to consider them because, at the end of the day, while nobody is questioning whether Twitter is an important social platform (it is), what it is in practice may be very different than what many of us have been told it is.