Bing and Google Deepen Social Integration in Search

Two different strategies. Bing do not have it's own social network, but has big influence on Facebook. Now who is really apart from owning a social assets is Yandex.com but they have a Twitter Firehose and, as Bing, can access Facebook data.

What strategy do think is the best? Being all-in-one Search+Social? Or make and acute search technologies and be friends with major Social networks?