Twitter had revenues of $317 million in 2012 and $269 million — 85% — came from advertising, which is almost the same as Facebook's revenue mix, 88% comes from ads.
The section of its S-1, "Our Value Proposition to Advertisers," doesn't mention Facebook once, but nearly everything that Twitter says makes it a distinctive ad-buy is also what makes it different from Facebook. It's a series of subtweets.
"Unique Ad Formats Native to the User Experience"
Twitter says that its basic advertising products, promoting tweets, accounts, and trends in users' timelines "provide advertisers with an opportunity to reach our users without disrupting or detracting from the user experience on our platform." The unstated premise: users can't stand Facebook's ads because they obviously get in the way of the basic Facebook experience.
This is a biggie. Less than a week ago, Facebook said it would reduce the number of ads that users clearly aren't interested in. The preponderance of, say, ads for religious dating services or dating services at all is a constant complaint among users. Twitter, on the other hand, makes a point of saying that its "pay-for-performance Promoted Products enable advertisers to reach users based on many factors." Specifically, Twitter says, because users can follow others without being followed themselves, the company has a clearer idea of what its users are interested in and then, how to best target ads and, as it scales up its advertising, avoid the constant complaints that have dogged Facebook.
"Earned Media and Viral Global Reach"
Basically, a tweet can viral way faster than a Facebook post. And even better, branded and advertising content can (and does) go viral : "the public and widely distributed nature of our platform enables Tweets to spread virally, potentially reaching all of our users and people around the world." Facebook ads, on the other hand, tend only to get really wide attention outside of Facebook when people are unhappy about them.
"Advertising in the Moment"
This is Twitter's truly unique sell to advertisers: people flock to Twitter during live events like TV shows and sporting events. So advertisers can target that huge surge in Twitter use from users who they know are intensely interested in one thing. This is why basically every phone company bought ads during the iPhone 5c and 5s presentation. Or as Twitter puts it: "Twitter's real-time nature allows our advertisers to capitalize on live events, existing conversations and trending topics." Facebook has been trying to claim the live mantle, but Twitter is very confident it dominates this space.
"Pay-for-Performance and Attractive Return on Investment"
An advertiser doesn't pay for a promoted tweet or promoted account, they pay for engagement: clicking links, replying, favoriting, retweeting or follows. Twitter says that "pay-for-performance structure aligns our interests in delivering relevant and engaging ads to our users with those of our advertisers" and implies that because of all the things you can do with a tweet, advertisers will be better able to track how users are engaging with them.
"Extension of Offline Advertising Campaigns"
Twitter says that its advertising "complements offline advertising campaigns, such as television ads. Integrating hashtags allows advertisers to extend the reach of an offline ad by driving significant earned media and continued conversation on Twitter." Basically, Twitter is making the case that only Twitter can get people to use something that only makes sense in its form (the #hashtag) offline.