With the exception of Twitter (which Google tried to buy), I think all of these companies are their natural enemies. Apple is a natural enemy of Google for the

With the exception of Twitter (which Google tried to buy), I think all of these companies are their natural enemies. Apple is a natural enemy of Google for the exact same reason Microsoft is - they don't want to see their products commoditized by web apps. The Apple/Google alliance was unnatural and only lasted as long as their common enemy did. Meanwhile, Yahoo and Facebook offer core services that broadly overlap with Google's (even pre-Google+). Both are competing for the same advertisers' dollars. And Facebook's deep social graph has been identified as a threat to Google's search for a long time.