Yahoo (YHOO) and Alibaba (ALBCF.PK) have officially closed their $7.6B share repurchase deal. Alibaba gets half of Yahoo's 40% stake back - it has the right to buy back half of the remainder if/when it IPOs - and Marissa Mayer now has $4.5B (post-tax) to potentially go acquisition-hunting with, following her decision to "review" plans to return the money to shareholders. Will Yelp (YELP) be in Mayer's crosshairs? Pinterest? Flipboard?