Twitter has been adding special iTunes preview panes to every tweet on Twitter.com for nearly two years. However, when the company first announced  that it would be working with Apple's now-defunct social network iTunes Ping, it didn't mention that it had joined iTunes' affiliate program, and has been adding its own iTunes affiliate ID to each of those links. As such, Twitter has been receiving a bounty (most likely the usual five percent) on all iTunes music sold via Twitter.com's iTunes preview panes.
Even now that iTunes Ping is no more, Twitter continues to insert iTunes affiliate links into tweets about not only music , but also apps . Twitter CEO Dick Costolo said he is thinking about  adding time-sensitive products such as concert tickets to Twitter's affiliate marketing program. Twitter is not currently running affiliate links for television shows , movies , or books .
A source familiar with the situation told Evolver.fm  that Twitter has been adding its own affiliate ID to links tweeted by users since it first launched that early integration with iTunes Ping, and that it continues to do so today. As we first reported  -- due to Evolver.fm's Knar Bedian  finding this preview pane while writing a tutorial  -- these links do not replace the ones in the main body of the tweet. However, they do replace the user's affiliate link in the iTunes preview area, pictured below:
Twitter's main focus is still said to be on advertising  and promoted tweets , trends, and accounts, rather than on becoming a large-scale affiliate marketer, which is probably a good idea .
We did learn something new today: that Twitter really is the iTunes affiliate "wdId=32800." When you purchase music or an app by clicking on one of these iTunes preview links, Twitter -- and not the original tweeter -- gets paid by Apple.
"When you click on a Tweet that's sent via Ping or that contains an iTunes link," reads the original announcement  about Twitter/iTunes integration, "you'll see the song or album in Twitter's details pane, with the ability to listen to song previews from iTunes, making the experience even richer."
It makes Twitter richer too, assuming people click through to buy -- though not enough for it to forsake its main strategy of including advertising in favor of becoming primarily an affiliate marketer, from what we hear.
Apple, Twitter, and Linkshare, which administers Apple's iTunes affiliate program in the United States, would not comment on the record. Arriving at this degree of understanding took quite a bit of doing:
- Twitter's New Revenue Plan: Piggybacking on Affiliate Links? 
- Twitter Is Not Piggybacking on Amazon Affiliates - Just iTunes 
- Twitter Is Probably the Biggest iTunes Affiliate in the World (Updated) 
- Twitter Is 'Thinking About' Ecommerce, Says CEO 
- Guest Opinion: Twitter Can Make Money from iTunes, But Its Power Is Overstated