@dougnewdick points out the risk of a company becoming over-dependent on Google. His particular example is prompted by Google's announcement that Google Reader will be discontinued.
I have previously commented on the subject of Creeping Business Dependency, the fact that many companies have allowed themselves to become dependent on a particular company, product or technology. Especially Google. If Google decides your website offends against some search engine rules, it is perfectly capable of making your website disappear from searches. (BMW disappeared from Google for three days in 2006 - see my post BMW Search Requests.) A company might well go bust before it could sort the problem out.
Of course, you can't avoid some dependencies, but I think it is important that any significant dependency should be clearly visible in the business architecture. (In general, business architects usually neglect this kind of dependency until I point out specific examples to them.)
When looking at this kind of dependency, it is important to remember the principles of asymmetry - the Product is not the Technology, and the Company is not the Product. There have been a few popular products and platforms whose owners lost interest - these included Bloglines (formerly owned by Ask) and Delicious (formerly owned by Yahoo) - but were revived under new ownership. Users of a popular platform may feel that a large user base provides grounds for optimism that someone will want to keep it going, even if the original owner doesn't wish to. However, there are many products and platforms that have not survived.
More fundamental is the question of the underlying technology. A few years ago, there was considerable confidence and investment in RSS and Atom feeds, and a number of products and platforms were developed to exploit this technology. If there is a healthy ecosystem of different products and platforms, with relatively low switching costs, it doesn't matter much if one product drops out. But if Google and others are losing interest in this technology, that's a much more fundamental problem for anyone who is heavily committed to it.
If Google stops providing a free service, those who really want it may have to pay to get a decent service elsewhere. But this alters the economics of the service ecosystem, with unpredictable consequences. Clearly there is a risk that the service you want (or the service you need your customers to use) is increasingly expensive, inconvenient and ultimately unavailable.
Doug Newdick, Cloud and Continuity of Supply Risk (March 2013)