"It combines low entry cost with high status and musical adaptability, and widespread availability of cheap instruction. Because of its ubiquity, expectations and standards of playing are generally fairly high (compared to many other instruments)."

Very well put Paul, I think you nailed it! However, the second statement puzzles me. I would have to rather agree with banjoman when he says ". . . its also a very easy instrument to make others think that you really can play it."

I can certainly vouch for that as I've fooled many people over the years. I am a flute player, but I think it is my general knowledge of music and instruments which allows me to mimic a guitar player on guitar. The standards of musical knowledge are quite low in our society, although I'm not convinced that it has ever been any different and even less convinced that it behoves me to complain about it. Nevertheless, most of our population have never taken any lessons, do not play any instrument, and do not read any literature on the subject - let alone read any music. That makes them poor judges of musical matters, including guitar playing. Over the years I have indeed found more accomplished musicians who play guitar than play, say clarinet, but I must say than when taken as a percentage of the population, I have not found very many of either.