As well as the mass of people getting their twitter accounts closed for using automated tools and creating lots of accounts, Twitter are also clamping down on the strategy many IMers are getting told for increasing followers.
You know - where you follow a bunch of people then after a few days unfollow all the ones who didn't follow you back, then rinse and repeat.
It's a pretty common way for marketers to try and raise their profile numbers rather than just being interesting and having people follow them.
Well it looks like Twitter are looking for people doing that now too.
So if anyone tries to sell you a completely automated tool, or a strategy for 'gaining xxx followers in xx days' etc... Be very careful - especially if you value your Twitter account.
You can read an article talking it this here: Dear Wanna-bes, Your Twitter Stardom is Coming to an End