Are you using it? Impressions? (same question for @svancermatthew)
From the FAQ I read:
Business model Our business model is actually very simple! We get revenue from ads and then share it with you - the user! You can buy premium to turn off the ads completely. We do NOT sell any of the user's data.
As I can understand they earn taking advantage of the Twitter's content, injecting their own ads. How can be permitted by the Twitter API TOS? Or is there an agreement with Twitter to show/monetize their ads?