Mt wife says it is one of the telltale signs of becoming a geezer :)
However, there might be more into it than senile ruminations of "back in my day" variety. Neuroscience tells us that human brain develops until the end of adolescence, and that development is profoundly affected by environmental stimuli. Different parts of brain are responsible for processing different types of stimuli, and the incidence of these stimuli affect the development of these parts. The parts of the brain used to process the frequent type of stimuli grow, whereas those responsible for processing stimuli that are infrequent or absent - atrophy. I thus follows that overstimulation of adolescent brain with a very narrow range of shock stimuli (noise, violence, explicit sex, outrage) by passive entertainment (movies, tee-vee) may lead to atrophy of higher-order cognitive functions (ability to stay focus, attention to nuance, analytical skills etc.). In other words, it is quite possible that the frequent exposure to idiot-boxes and shock-kultur does make kids dumber by atrophying their brain functions.
PS. I understand that saying anything bad about pop-kultur on this list is a blasphemy and is likely to provoke angry reactions (which I kind of like, since I enjoy shitting on altars) - but try to be rational about it. We are eager to admit negative effect of environmental stimuli (pesticides, nukes, tobacco, industrial pollution, pharmaceuticals, poverty, etc) on human body - so why rejecting such effects of other stimuli. Just because we like the latter and dislike the former?
Wojtek