When will someone acknowledge that the enormous popularity of the Beatles and Sgt. Pepper's Lonely Hearts Club Band was as much a consequence of opportunity  and demographics as it was musical artistry. The year was 1968  and tens of millions of Baby Boomers (now outnumbering their parents and  grand parents) were teenagers with spending money in their pockets.  Teenagers had been buying rock'n'roll records since Bill Haley and the  Comets released `Rock Around The Clock.' But the 60's decade was different:  never before had there been so many kids with so much cash (economists call  it `disposable income'). Teenagers bought fast cars, fast food and millions  of those black vinyl things.