In the world of business everything is very relative, and former friends turn to become competitors and later enemies. As the cruel market doesn't support any relations besides the profit margins and revenues growth, some stable good relations are impossible. And to climb the top positions the companies are ready to sacrifice many things.
However, in the tech world, of course, companies can cooperate and compete at the same time. For example, Apple and Microsoft have competed with their operating systems while Microsoft did not stop to make a top-selling suite of Mac office software. In a similar way Google is sure to make its products work with Microsoft's Windows OS, neglecting however hard Schmidt's company tries to push the desktop OS off the mainstream market, shifting users' interest to the web OS and cloud computing.
Everything at the market is very vague. Yesterday's friends become relatives while sworn enemies begin working together and demonstrate the whole world what a splendid couple they are. It is particularly true for the high-tech industry. Google and Microsoft seemed to be extremely good friends sharing almost everything while Microsoft was viewed like a kind of personal Apple's nemesis. It used to be just 4 years ago. No the situation has drastically changed.
Apple and Google have split up, each following its own path and trying to bite a bit of the other's pie. Google was a big web company known for its web services and a growing cloud computing initiative, while Apple was happy with making sleek and posh handsets that appealed so much to common users. They had practically nothing to divide but lots to share.
4 years since those good old times and the situation is vice versa. Only a lazy blogger or tech journalist has said nothing about these sworn friends' relations. Google has launched the Android platform, a bit clumsy at first like a new-born puppy but gaining ground with every new iteration. Apple has become particularly interested in web advertising market striving to catch up with Google. In addition the companies do not miss any chance to play a dirty trick on each other or each other's allies. In general, they seem to behave like a divorced couple being unable to forget each other as well as to forgive the mutual betrayal.