You mean like telepathy? You do realize about hundreds of people die every second, right? If everyone was linked for fifteen minutes, they'd all have to experience death over and over and over again, not to mention rape victims overwhelming emotions, the starving children's overwhelming hunger and pain, tons and tons of grief, and lots of pain from people who are in hospitals suffering from some kind of illness.
The happiness, which is a fragile emotion for all of us, would be completely shattered by the overwhelming influx of pain, fear, stress, death, and other horrors filling the earth. Heck, sharing the thoughts of someone who has taken pleasure from raping a child, or enjoyed murdering someone, maybe even eating them afterwards (cannibalism isn't completely unheard of, even in this day and age). Would you like to have those memories, knowing what it feels like to be in that position?
I think that if the experience of being telepathically linked to everyone in the world didn't kill all of the human race, we'd all commit suicide afterwards, from the sheer pain of what we knew. Not too many humans can function while knowing the true horrors of the world. So, they ignore them, and go on with their lives. Forcing them to acknowledge those horrors would be catastrophic for their mental health.
Interesting question, anyway.
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