how much knowledge

Is there any estimations about how much knowledge a typical man has?

If "everything normal" (level where man normally functions in society,
forexample he would know few different insect species, not few billion
different) would be modeled as objects, How many classes would there be?

Or how about from point of relational database, how many gigabytes would
humans knowledge require?


Has anyone tried creating a huge system like that, and letting it run
against database similar to google, to create connections between different
classes, making them stronger, according to how often they appear together?