Twitter made its ad a tweet, so it went everywhere tweets go, mobile included

In a February 2015 WIRED feature, Twitter's executives describe how the company went from "zero dollars and zero cents" in revenue when Dick Costolo arrived as COO on September 1, 2009, to the $1.375 billion it estimated for 2014. Costolo says a first move was selling Google and Microsoft direct access to the data firehose, but he saw advertising as the future.

Kevin Weil's five-person team built the ad product. The idea, which WIRED credits mostly to early employee Anamitra Banerji and his November 2009 memo, was that the ad would be a tweet. Weil says people asked why Twitter did not just put AdSense on the side of the page, but the team wanted something that felt like Twitter. Costolo says an ad can go everywhere tweets go, and that favorites, replies and retweets could signal how far to broadcast it.

Twitter went slowly. The first Promoted Tweet, from Starbucks on April 13, 2010, appeared only in search, one of six charter customers with Red Bull, Sony Pictures, Best Buy, Virgin America and Bravo. They paid nothing for a month or two, and the first dollar came in June. Advertisers buy by auction, borrowing from Google AdWords, and payment is triggered only when users engage with the ad through retweets, replies and similar actions.

Most users reached Twitter through third-party apps, so an ad had to follow the tweet wherever it was shown.

A banner beside the timeline would feel foreign and cost users' goodwill.

Starting in search and with six big brands let Twitter watch user reaction before charging.

Engagement-based pricing made the ads low-risk for advertisers and welcome to users.

Fit the revenue unit into the product's native format instead of bolting a foreign ad slot beside it; the ad then rides every platform shift.

Weil says the ads-as-tweets design made the shift to mobile seamless, and that Promoted Tweets automatically gained features such as photos, video and app downloads. WIRED reports Twitter did hit roughly $1.375 billion in 2014 revenue, more than doubling year over year, though it was not profitable and its user growth fell far short of early goals. The excerpt of the article provided ends before describing later products.