What’s the most uncool word in social media?

Advertising.

Just look at the pains the top social networking companies take to avoid uttering the dreaded term.

Twitter started the trend when it rolled out its advertising products in 2010, which it dubbed “promoted Tweets.” Chief Executive Dick Costolo (who was COO at the time) insisted that the marketing pitches coming to Twitter were not ads at all – they were simply standard Twitter messages that companies could pay to promote.

Now Facebook, which derived 85 percent of its revenue from advertising last year, has developed a similar aversion to the A word.

At a splashy marketing event in New York on Wednesday, the company introduced a new ad format that will allow big brand marketers to push information directly into users’ newsfeeds and onto other prominent on-screen real-estate. The word “advertising” was conspicuously absent from the somewhat vague name of the new ad format: “Premium on Facebook.”

Facebook executive Mike Hoefflinger (pictured, right)  even delivered a whole on-stage spiel about why Facebook’s new ads were in fact not ads, but “stories.”