The second reason why DDoS could become an issue is that domestic Internet connections are becoming blazingly fast, making it easier to launch successful attacks, especially if botnets are involved. (Botnets are networks of innocent hacked computers that participate in hack attacks without their owners' knowledge.)
For example, high-speed fiber optic Internet connections are becoming more common in the western world. Verizon currently offers 150Mbps connections for business. That's an astonishing data rate unthinkable for small-scale connections just a few years ago. On its own any computer behind that connection could be a formidable denial of service attack agent, but can you imagine the effect if hundreds if not thousands of computers, each with a similar high-speed connection, were used to launch an attack? If fiber to the home and business become commonplace and cheap--as it undoubtedly will--this is sure to happen.
The third concern is the growth of mobile computing devices. Cell phone infrastructure is expanding at a rapid rate, essentially creating a second-tier wireless Internet. Speeds are getting faster too as 4G services are rolled out. There's no reason why mobile devices can't join in DDoS attacks launched by their desktop brethren.
However, of all the recent trends, this is the least concerning. Right now there have been no reports of phones or tablets being used to launch DDoS attacks, and the programmers behind operating systems such as Apple iOS and Google Android are working hard to keep it that way by building in security features. After all, they have the benefit of hindsight that wasn't available to designers of the PC. However, hackers have consistently shown that where there's a will, there's a way.
It'd be terrific if IPv6, the new Internet routing technology that we're going to switch to real soon now, had DDoS protection. However, although the new security systems in place with IPv6 offer protection against certain kinds of attack, it's still a gloomy outlook. DDoS is still entirely possible.
Denial of service attacks have been popular for as long as the Internet has been mainstream, and have shown similar kind of growth patterns. However, it might just be that, through a combination of societal changes and domestic technology improvements, they've begun to evolve faster than we're able to cope with.
Keir Thomas has been writing about computing since the last century, and more recently has written several best-selling books. You can learn more about him at http://keirthomas.com and his Twitter feed is @keirthomas.