Ask HN: Which other large tech companies should Yahoo buy?

Let's fantasize, which we properties should the large tech (Google, Facebook, Microsoft, Amazon) companies buy next? Yahoo is on a buying spree and will do many more, so the competitors should prepare as well. Yelp? Viber? Pinterest? Path?

From the mega deals, either Apple, Microsoft or Google should try to buy Facebook and not settle for Twitter.

On enterprise front, there is potential for someone to start acquiring many smaller B2B tools and integrate just their salesforces, while keeping the services independent.