In a blog post last Monday, Twitter had announced its acquisition of the online mobile-ad exchange MoPub. The financial terms of the deal were not disclosed however a source said that Twitter paid USD350 million in stock for MoPub. The source asked not to be identified as the matter was held private in nature.

The same source said the deal had assigned a value of approximately USD20 to Twitter shares. This was even MoPub's shares had been trading higher than the USD20 value on the secondary market.

MoPub is a hosted ad serving solution that was built specifically for mobile publishers. The company's services allow companies to be updated of ad inventory in real time. This was similar to DoubleClick, the microblogging service offered by Google.

MoPub is backed by venture firms including Accel Partners, Jafco Ventures and Harrison Metal Capital.

Twitter had been considered a hot initial public offering target for 2014.