I've added some new sub-categories to the reports.
App Spam
Accounts where more than 50% of their tweets are auto-generated by an application. Examples of this include paper.li, 4sq, blip.fm, RunKeeper, miso etc.
Uses Advertising Networks
Accounts that are being paid to put tweets into their stream. Advertising networks include organisations such as MyLikes, ad.ly, Magpie, Sponsored Tweets, etc.
Self Obsessed
Accounts where more than 50% of the tweets are about themselves. So, either starting their tweets with "I", "Ive", "I'm", "I'd" or retweeting things people have said about them.
Relatively Unpopular
People who follow more than 3.3 times as many people who follow them. Or, put another way, those who have fewer than 30% people following them back. Sometimes this is just because someone likes to follow lots of people, but occasionally it can also show someone (eg spam bots) whose behaviour is offputting or boring, so very few people choose to follow them back.
The Self Obsessed and Relatively Unpopular sub-categories go into a new category, called "Not Very Interesting." It will appear at the bottom of your reports.
As always, this is informational. It's always up to you who you want to follow.
Personally, I follow (& will always follow) a whole bunch of people that appear on my report. Why? Because they're entertaining, informative and I like them. Free will - it's not an accident!