Advertisers will be able to find tweets on a key topic; including who is tweeting when and what other actions the tweeter is taking while the conversation is active. With an ad server integrated in the process a targeted message may be dropped into the Twitter conversation at the appropriate time. Finally, Twitter will be monetized, for good or bad,
Marketing: Yahoo Pact Gives Twitter Distribution, Revenue - Advertising Age - Digital
It's the latest step in Yahoo's latest strategy, which is to integrate the world's most popular social networks into the Yahoo environment rather than try to compete with them. The pact is similar to a deal with Facebook announced in December, allowing users to import their connections and update their status through Yahoo.