These are known spammers and other morons on Twitter. What is a Twitter spammer? Measure a user's ratio of how many they follow to how many follow them.
Those who have panicked that their Twitter followers have dropped - don't be paranoid! The twitter spammers have again taken the axe. Twitter self corrects about every 90 days and you'll get used to it.
The fact is that Twitter is for meaningful, authentic communication - albeit short and if you do that, it can be a fun, and useful part of your personal learning network. It is unique to you and how you want to do it! Remember that it is not about the followers although you'll have people direct message you that you can somehow buy 200 or even 500 followers a day -- like that will enrich your life! Come on -- twitter is great and it is not about how many people follow YOU anyway - if you get tied up in that too much then you're probably really there for just selfish reasons anyway. Enjoy and have fun!
Did you notice a big drop in your Twitter follower numbers yesterday? It seems that the Twitter team recently decided to step up their Twitter spammer detection, and, in typical Twitter fashion, their algorithm sent the service haywire, leading to yet another sighting of the Fail Whale while the issue was resolved. Meanwhile, Twitterers everywhere were in an uproar over their lost follower counts.
TrueTwit is a validation service for Twitter. It distinguishes between people and bots, helps prevent spam, and SAVES YOU TIME in MANAGING (BLOCKING) BAD FOLLOWERS!