As my astute colleague Laura had cause to mention today — if you’re using a free service without paying anything, you’re probably the product. Twitter, long the bastion of those averse to the marketing tactics already displayed on social media sites like Facebook, has announced it’s going to start taking users’ tweets and aiming ads at them based on the content.

Twitter already isn’t without ads — companies have been paying to have their tweets promoted for a long while now. But this new system will let advertisers target users directly after combing through their indicated interests. Promoted tweets are going to cost advertisers a whole less, too, at only one cent.

Google’s used this tactic for a long time already, pushing ads for certain products based on what users email about or search for on its search engine. Meanwhile, Facebook got into hot water over pushing “Likes” as Sponsored Stories, turning its users into unpaid marketers.

On the new Twitter, companies will be able to send paid ads as tweets to entire groups of users according to more than 350 interest categories handled by Twitter. The new ads will let companies get at a “very narrow, very specific and incredibly focused audience,” Kevin Weil, a Twitter director of product management, said in an interview.

It sounds sort of like when you get a Twitter spam bot offering you hot deals on electronics after you tweet to complain about your shoddy laptop. Annoying, especially as many people get excited when they’re notified about an incoming interaction, only to be disappointed with spam.

Many users are already wary about tweeting certain key words in order to avoid such bots, so this ad system could lead to a lot more self-censorship as a way to remain untargeted and unmarketed to. Good luck in the trenches, everyone.

Twitter’s new ads now target user interests [Reuters]

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.