The Expo Passport

Back in 1967, the Expo passport was created for the World Fair that year. The details are: designed like a regular passport, space to be stamped for each of the represented countries. It has been somewhat popular in the past, yet at far less crowded World's Fairs, they have been fairly easy to fill and acquire. Not so at the Shanghai World Expo 2010.
In the beginning, maybe 50,000 were sold per day because the demand was vastly underestimated. If you have 350,000-500,000 people in one place with a 30 RMB passport that can become a pretty souvenir with intricate stamps from many of over 200 pavilions (handed out for free) would you imagine that 50,000 would be enough? Exactly, it wasn't.
The next item to consider is the wait line for some pavilions:
Saudi Arabia pavilion (largest IMAX screen in the world showing a 10 minute movie): >4 hours on average day, close to 8 on busy day;

Japan pavilion (violin-playing robot, Japanese-Chinese cross cultural opera, new technological advances in touchscreen technology and big screen tv, etc): >6 hours every day, always full line;

China pavilion (movie about Chinese history, display of changing nature of Chinese home through the decades, gigantic computer-animated Chinese scroll with intricate scenes that change as you walk, etc.): reservations for one of 50,000 entries disappear within 45 minutes of park opening

USA pavilion (3 movies about our country): 1.5-2.5 hours

Several other countries have very long wait times, such as Germany, Italy, etc.
The point of this is that you must wait in line several hours to get stamps for your passport, and many of them limit stamps to 2-5 per person.
What need would they have to limit the number of stamps, you ask? Several reasons:
Everyone has a friend, relative, classmate, etc. who could not afford the time or money to come to the Expo, it takes a lot of effort and persistence to wait in line/fight your way through it to achieve the stamps, and they can be sold for money.
That's right, a complete passport can be sold for tons of money: most recently, I heard they go for 6,000 RMB ($880.75)!
Here's the problem: the stamp is a big hassle for no reward. The expo bureau makes 30 RMB per passport, but they do not reimburse pavilions for their ink expenditures; people rarely care for their exhibits and go straight to the stamp line; it is so coveted that fights can break out between people who don't want to wait so lines to the stamping stations must sometimes be guided and roped off. Some staff members from countries like Mexico and Slovenia have personally expressed desires to return home rather than stamp passports every day for hours. I can't say I blame them.