Thinking about privacy, today it ocurred to me, that this concept might get completely abandoned in the future. What would happen, if we all become one big brain, where everybody has full access to everybody elses information? Apart from feeling weird at first, would there be any serious downsides?
If there is only one big brain, "WE" won't exist anymore. There will only be "I". In Richard Dawkins'book, The Selfish Gene, he explains how organisms are only vehicles for the genomes within them and how genomes tend to compete for resources and how they could be described as essentially "selfish". For that reason alone, it is very unlikely that "we" could turn into an "I". On the other hand, genomes are just another way to transmit information, and mankind has created other kinds of information, entirely separate from biological processes. Maybe it will be that information that may give rise to "One big brain" but it will be a whole new species, if it is allowed to exist, unless we learn to live along symbiotically. Even then, once an artificial species emerges, others may emerge too (see Tom Ray's Tierra experiments) and those may exist entirely separate lives from the symbiosis.
I personally like to think of the human race as a giant super computer with local caches in brains and quite slow information transfer. It even has bad/malfunctioning cores.