Well, when you consider that the parents of as many as 1 in 5 children have been persuaded to drug their kids, you can't help but conclude that many adults will be suckered into thinking they have the 'disorder' as well.
Have to wonder if some of the attention deficit is due to tv progamming and magazine reporting going to short attention spawn audiences. There is probably a statistic of how long a typical radio listener leaves a station on before switching the dial. CDs give us instant gratification to go to a specific cut or a specific part of a specific cut of an album.
Another factor may be past history of drug use (especially things like esctasy and LSD which can affect brain chemistry).
People "multitasking" (listening to radio/tv/conversation while surfing the web, posting to FR, or reading the newspaper or a magazine) may also be a factor in being able to devote focus to just one task. We've become so used to tuning out outside distractions that we may not be able to concentrate when they aren't present.
I've been in bars that have low music on (a stereo or a jukebox). Conversational volume continues to rise until people can talk over the music or each other. When the CD player is off (or the jukebox runs empty) the conversational tone will stay up at that high level for awhile (I've pointed it out to some friends; the conspicuous abscence of background noise).
Our modern society may be the cause of the problem (but a lifetime routine of prescription drugs isn't necessarily the answer). May explain why this wasn't an issue a century ago.