Kara Swisher is reporting that the rumors about Facebook acquiring Twitter were not only true, but that talks between the microblogging company and the social-network site broke down three weeks ago. The social net was offering to acquire the company for $500 million of its stock, but Twitter execs and investors apparently believe the company should “take a shot” at building revenues “as well as it [has] done building its growth” and not just jump at the first chance it gets to sell the business. Of course, there was also the matter of price—or, in this case, is half-a-billion dollars worth of Facebook stock really worth half-a-billion dollars? Facebook was pricing the transaction based on its own $15 billion valuation following Microsoft’s investment in it. But Twitter believed a more accurate valuation was $5 billion, making the deal worth $150 million.