I think it will be the spread of the internet. At the end of the 90s the net was still a bit of a novelty, that while many people had access to it, its had not become a major part of life as it did not have that many mainstream uses. By the end of the 00s the internet had become mainstream and had revolutionized the way many of us communicate and spend our leisure time not to mention the way that we work and study. Whether that be spending time on Facebook, watching TV or films online and doing shopping online. By the end of the decade many of our devices were connected, and dependent on, the net from smart phones to Games consoles, and many of these would not exist in their current form if the Internet had not taken off in such a big way.