Fake Twitter followers are on everyone’s mind. Last month, GOP Presidential candidate Mitt Romney’s Twitter followers jumped substantially overnight, leading some to accuse the campaign of buying followers. They denied it of course, but it led to a much more prominent discussion of the somewhat depressing reality that many of your tweets may be falling on deaf ears. Deaf, fake ears.

A recent study into the “Twitter Underground Economy” demonstrated just how easy it is to buy fake followers on the site. The study found that the average cost of buying 1,000 fake followers was about $18, and the average user who buys fake followers has about 48,885.

When we say “fake,” we mean fake – accounts conjured out of thin air for the sole purpose of boosting follower counts and egos. They can also be used as retweet factories, but then again, who needs a fake account with no real followers to retweet your tweets anyway?

Twitter has a little over 140 million active users. CEO Dick Costolo said so a few months ago. But some analysts have claimed that Twitter has over 500 million registered accounts. It doesn’t take a mathematician to see that that’s a huge percentage of inactive users.

It’s pretty clear that Twitter is full of fake and inactive accounts. That’s not debatable. We thought it would be fun to look at the top 10 Twitter accounts (according to number of followers) and see just how many of their followers are fake and inactive.

Lucky for us, Status People has just released a new tool that allows any Twitter user to check their (and their friends’) follower breakdown.

“We take a sample of your follower data. Up to 500 records depending on how ‘popular’ you are and assess them against a number of simple spam criteria,” says Status People. “On a very basic level spam accounts tend to have few or no followers and few or no tweets. But in contrast they tend to follow a lot of other accounts.”

They also say those with 10,000 or less followers will get the most accurate breakdown, but they feel confident that their tool is accurate for all Twitter users. Of course, determining what is and what isn’t a fake account isn’t an exact science, but Status People’s tool gives us a nice insight into how authentic these massive celebrity Twitter followings really are.

We looked at the top 10 Twitter accounts in terms of follower count, and we found that that 27.1% of their followers are listed as “Fake,” on average. And a whopping 40.5% of the accounts are said to be “Inactive.” That means that only 32.4% of the accounts that follow the top 10 Twitter accounts are “Good,” legitimate users.

Twitter Queen Lady Gaga only registered 29% “Good” followers.

The star of the top 10 was Kim Kardashian, who registered 44% “Good” followers and only 18% “Fake.”

Note: The top 10 Twitter accounts in terms of followers currently belong to (in order) Lady Gaga, Justin Bieber, Katy Perry, Rihanna, Britney Spears, President Obama, Shakira, Taylor Swift, Kim Kardashian, and YouTube.