the world's total yearly production of print, film, optical, and magnetic content would require roughly 1.5 billion gigabytes of storage. This is the equivalent of 250 megabytes per person for each man, woman, and child on earth.
http://www2.sims.berkeley.edu/research/projects/how-much-info/
估计现在（2010）每个人平均产生的信息量就不只250M,而是2.5G了吧