Welcome to the brave new world of Twitter advertising, in which companies will be able to target you based on the content of your tweets. Seems that zeroing in on users based on who they follow just isn't good enough, so the micro-blogging service is now in the business of selling "keyword targeting in timelines." The new feature just rolled out in all markets covering 15 languages.

But, emphasizes the company, users won't have to contend with more advertisements than usual being foisted at them. The system is supposedly able to discern their interests and deliver more relevant ones that can even distinguish negative feelings. In other words, if you're tweeting about a dislike for Pepsi or retweeting someone's bad experience with Dodge, you won't see Promoted Tweets for those companies. And if things somehow do pop up that you don't want, you can easily dismiss them.

Understandably, this is exciting news for advertisers. Not only does it tighten up a rather vague way of ad-targeting — using location, platform or people you follow — but it can also dish up relevant promotions in the very moment when you've expressed interest in them. Anyone who has ever received a restaurant coupon when they're hungry can attest to the power of that kind of timing. And if there's one thing Twitter is good at, it's gauging and delivering real-time sentiment.

Of course, such a system has the immense potential to freak users out as well. I've seen people tweeting about extremely personal things, like a wayward husband or wife. In this scenario, those folks might instantly get promotions for divorce lawyers in return. Yikes.