What follows is an extension of thoughts began in an English class not so long ago, debating the benefits of telepaths over regular humans. And so it follows...
If everyone possessed the ability of telepathy, broadcasting our thoughts endlessly and indiscriminately, we would lose all individuality, being inable to tell the differences between our own thoughts and those of Farmer Bob in Kalamazoo. We would revert to a hive-like society, with the most powerful telecasters taking the role of "Queen".
Bands and parties would be organized to gather food for the good of the collective entity of mankind, and everyone would lose their individuality. Knowledge would be free to everyone, but knowledge without responsibility is dangerous. Efficiency would rise to fantastic amounts, as everyone would have the knowledge to perform any skill or task imaginable.
Everyone would be fed and happy, and without a need for personal gain, people would lose their higher instincts and become sex beasts, existing only to run machinery and "service" the Queens, or breeding stock. With this uncommon work ethic, the earth would be stripped down to its bare bones, so to speak, within a matter of generations, in the search for more natural resources to supply us with a yet larger food supply for the exploding population, reproducing time and again for the betterment of the race.
Eventually, the earth would become unfit to raise food, the cause being through pollution, lack of mineral resources, or overpopulation. A planet this size simply cannot support an ecosystem growing at that rate, that takes everything out and gives nothing back.
This is where it starts to get weird.
With no source of food production, we would be forced to resort to cannibalism and the few strong hunter humans would end up becoming a master race of human-eaters. The masters would breed and the food people would be rendered sterile, so as for survival of the fittest. The food people, of course, would willingly fatten themselves up and wait in line to the slaughterhouse knowing that all was for the ultimate betterment of the species.
However, as the food stock wouldn't be allowed to breed, the small group of masters woud eventually inbreed themselves to the point where they had 4 heads, 8 fingers, and a hamster named Bob growing out of their ear. Without the leadership of the hunters, the food stock would happily eat until they popped, as, being all sterile, they would not be able to continue the race.
Of course, much of this is still possible, even probable, even if mankind is NOT rendered telepathic through some strange mental disorder. What a cheery forecast for our future, eh? A planet full of buffed, muscle-bound idiots, and happy placid sheep who do what they're told.
Wait a sec...