Twitter started putting promoted tweets in users' timelines this summer, but was careful to note at you would only see them if you followed the brand. Since you'd be seeing those brands' tweets anyway, the only difference you'd notice was that some of those tweets were "sticky," meaning they would stay at the top of your timeline until you read them.
The arrival of promoted tweets from companies that are similar to the companies you already follow is hardly unexpected. AllThingsD predicted it a couple of weeks ago.
But what Costolo revealed Thursday was that everyone would start to see promoted tweets in their timeline, regardless of how they're accessing Twitter. Doesn't matter whether you're on the company's mobile client, Twitter.com, or a third-party service like TweetDeck. Ads are coming to everyone.
This was inevitable; Twitter decided long ago advertising would be its main source of revenue. What matters is how the rollout of promoted tweets is handled. And Costolo seems to be erring on the side of caution. Promoted Tweets, when you see them, "will be based on the interest graph of the accounts you follow," he says. "So you should be seeing the kind of content you’re already interested in.”
We'll wait to see the actual rollout before passing judgment. But from Thursday's evidence, it seems Costolo is handling this crucial transition in the best way possible. He cares deeply about the product and knows that its health comes first. (Revenue, Costolo says, is like breathing: it's vital to life, but it's not the purpose of life.)
Hence those eye-popping engagement stats. Costolo had to prove that Twitter is thriving under his management, and so it is. Compared to the beginning of 2011, 110% more tweets are being sent every day now; the number of active users the service expects to add by the end of the year -- that is, in the next four months -- outranks the total number of users it added between 2006 and 2009.