Why do the Dutch keep their curtains open?

Source: The Xenophobe's Guide to the Dutch

The Dutch are open about everything. Preserved vegetables come in glass jars rather than in tins. Lavatories have a shelf in the bowl, ensuring that even your internal workings are open to daily inspection (the one German invention the Dutch have taken to with relish). To assure their neighbours, and themselves, that they have nothing to hide, the Dutch build houses with big windows and do not draw their curtains at night. You can watch your neighbours' television, see what they are having for dinner, note whether they shout at their children and fervently exercise your powers of tolerance if you notice anything untoward. 

Clean windows are the primary concern of any house holder, and rooms are lit with a subtle chiaroscuro that presents a cosy picture to the street at night. Rather than draw the blinds, people whose houses open directly on to the street hang little screens made out of wooden-framed doilies in the windows, or stick narrow strips of clouded plastic to the glass. These are positioned to avoid tiresome eye-contact with passers-by, while still leaving the room open to public view.

No Dutch person would dream of staring in at the windows. That would be an invasion of privacy. Curiously, it was a Dutch television company that first came up with the idea for Big Brother, the show that allows millions to be Peeping Toms. This is the ultimate expression of Open Curtains, while spicing things up by breaking the paramount social taboo.
When this openness spreads to personal relationships, it leads to a perfect frankness that other nations may find disarming. If you are suffering from a particularly unfortunate haircut, an English friend might tactfully suggest that you wear that nice hat you bought last week. A Dutch person will ask you what on earth has happened to your hair.