Twitter's business model: profitability thanks to search engines?

The little bird grew up. Since its creation in 2006, the social network has become more and more popular to reach around 60 millions users. The only shadow was the lack of revenue. It was said that Twitter was very successful but had no business model. There was this discussion about how Twitter could make money to be able to at least, cover its costs. Advertisement was mentioned but people feared it could make Twitter be less attractive and loose users. I thought Twitter could earn money by providing precise web analytics services for companies. Hence, many businesses use Twitter to promote their activities, but it's hard to quantify to what extend your tweets are seen and reach the targeted audience. I still think there's big money to make this way. But that's not how Twitter succeed in earning money. Twitter signed an agreement with Google and Bing to let them use the twittosphere to deliver in real time results. It seems that thanks to these agreements, Twitter reached the breakeve