I started this thread about 18 months ago.
My husband used to work at Microsoft until recently and he researched this issue inside the company as well as he could. The real problem is that the antenna is placed right behind the top front of the screen. If the lid is fully closed the antenna is basically inside a metal enclosure and subject to a "Faraday cage" effect, the same reason for losing cell phone signals inside an elevator. The magnet on the lid may make it even worse.
The engineers that designed it must have not had a clue that users would like to have a nice, uncluttered desk with the Book out of sight.