During one of the recent Application Security training courses I delivered recently, one interesting example I gave during a section on "Our dependencies on Technologies and Frameworks that we don't fully understand" was the concept of how much of a threat to the UK economy is Google?
For example if Twitter or Facebook were not available from the UK, I don't think the impact would be significant.
But if Google and all its services (search, mail, calendar, maps, geolocation, docs, spreadsheets, contacts, Google ID) was suddenly not available, I bet that there would be a significant disruption to a LOT of individuals, business and government agencies.
There is a lot of talk in the UK about the Geopolitical threat of Russia (and its control on natural resources used by the UK), but I'm pretty sure Google can do more damage.
Of course that it would be economical/business suicidal for Google to do such a thing, but that doesn't make it less real or dangerous.