Hot data: An IT technician checks the network servers at a data farm. Alamy Photograph: Juice Images/AlamyPhysics has Newton's first law ("Every body persists in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed"). The equivalent forinternet services is simpler, though just as general in its applicability: it says that there is no such thing as a free lunch.The strange thing is that most users of Google, Facebook, Twitter and other "free" services seem to be only dimly aware of this law. F...