...a more likely explanation for limiting the number of visitors is continuing concern about adverse publicity at a time of Tibetan unrest.
Another possible explanation for restricting numbers on Everest: supply and demand. The Chinese may be hoping to raise peak fees again by limiting the number of permits. Currently, peak fees on Everest are much higher on the Nepali side of the mountain. In Tibet the fee was just $4,900 per person in 2007, the last time the mountain was open. But the fee jumped more than 60 percent that year.
Read more on Dougald MacDonald's Blog: The Mountain World
Discovery Channel News Item: Limit on Everest