Fibre optic submarine cables carry the vast bulk of Internet and other communications traffic between continents. If you - by which I mean your government - wanted to access the information flowing through these, then the location of the cables is important - relative to where your government has (military) bases or national jurisdiction.
It is striking that the bulk of the transatlantic cables go through the UK, and the other continent-connecting ones that don't tend to go through places like Cyprus, the home of a British military base. Isn't it nice to know we are all 'connected' - probably at most just one or two junctions away, at least from GCHQ?
Take a look at the submarine cable map, of which a portion is shown below. The full world map is available from here - scroll in/out from this site (not from the image below) to get a smaller/bigger geographical picture, or from a different central location.
This is the physical infrastructure for Edward Snowden's story.
Tony Norfield, 19 September 2013