After months when markets have oscillated on the ebbs and flows of political tumult in the Middle East and natural catastrophe and near-nuclear disaster in Japan, the business world was pleasantly rocked by the announcement of a mega-deal: the planned $39 billion acquisition of T-Mobile USA by AT&T. If the deal is approved, AT&T will add nearly 35 million new subscribers and vault past Verizon to become the largest wireless carrier in the United States with about 129 million customers, surpassing Verizon’s 100 million or so.