How many of my Twitter followers are fake?

Microblogging service Twitter has done a good job of getting rid of spam accounts that follow Twitter users.
After I signed up for Twitter in April 2009, I used to get a lot of questionable followers. Many of them featured photos of attractive women. If you checked out their profiles, you would find weblinks that led to shady e-commerce sites like dating services and online pharmacies.
By late 2010, those types of spam followers started disappearing as Twitter cracked down on them.
Twitter still has a major problem with spam, but at least they don’t follow people any more. Instead, they’ll post something with your user name, along with a spam weblink. These show up in the Connect section on Twitter. Whenever I get these, I report those users for spam.
A much bigger spam problem can be found when you search Twitter, especially for trending topics or news events. These spammers will use keywords or hashtags to spread their spam weblinks.
StatusPeople.com has created a tool for checking out how many of your users are fake or inactive. I tried the Fake Follower Check and found out that 3% of my 530 followers are fake and 15% are inactive. That leaves 82% rated as “good.”