Google is here playing the same defacto regulatory role as a stock exchange - if you want us to list you, please play according to our rules. (Google can therefore add extra rules to those rules imposed by national or international law. Whether Google can subtract rules is of course an entirely different and perhaps even more controversial question.)
But there is a crucial difference. With a stock market, there is a documented agreement between the stock exchange and the listed company, and any disputes can be taken to legal process. However, it is difficult to see how any company, however large, might establish in law that it had been unfairly treated by Google in such a matter. Even if there was clear evidence of financial loss as a result of a material change in search ranking, it would probably be impossible to pin liability for this loss onto Google.
Look at BMW's position from a service-oriented perspective. BMW's promotional and marketing capability is critically dependent on Internet search services provided to BMW's customers by Google and its competitors. This is of course true of many companies, large and small. But for most or all of these companies (and I presume this is the case for BMW), there is no formal contract with Google that governs this particular dependency, and no defined service level agreement.
Google's published statements appear to offer some comfort, implying that it will only take this kind of action against a company in response to some detected non-compliance on the company's part with Google's rules. (We can interpret these statements as part of a
Bottom Line: If you are dependent on a service you don't control, then there is a risk that needs to be managed. In a service economy, there will be many services that you want to use, because the potential rewards of these services are well high enough to justify the risks. But these risks still exist, and service management needs to include proper attention to the relevant risk factors.