Postage stamps proved to be a vital technological innovation. In a world where most innovations are beyond the ability of most of us to understand let alone initiate ourselves, the obviousness of most technological innovations before 1900 is shocking. Look at the variations of plough technology and agricultural yields (http://en.wikipedia.org/wiki/Plow). throughout history. These simple changes made monumental differences in living standards.
Our little gummed tabs of paper produced a revolution in communication that in depth and scope rivalled only the Internet of today. Before the Penny Black, to send a letter a writer had to take it to the post office, have it weighed or rated and decide whether to prepay it or have it sent postage due (most letters were sent postage due to insure that they got there). The postage stamp which demanded prepayment eliminated several steps of expensive handling and dramatically reduced post office costs. Lower costs meant lower postage which in turn meant higher letter volume and vastly more communication. In Great Britain alone, where the population was already quite commercial and making ample use of the postal system and where postal rates were low compared to the rest of the world, letter volume increased threefold in the two years after the introduction of the Penny Black. Other countries saw far greater increases in communication as postage rates went down due to the efficiencies of prepaid postage. We take this for granted now 170 years later, but just as much of the economic success of the 21st century will be laid to the computer, much of the economic success of the nineteenth century was the direct result of Rowland Hill and his Penny Post.