Stuart Anderson has an interesting op-ed in the New York Times, presenting a strong argument in favour of getting more foreign students into American universities.
... [W]ithout international students, certain science and engineering programs could not be offered at many American universities, because the foreign students populate classes and serve as teaching assistants. They also go on to supply faculty for those programs. About one-third of America's engineering professors are foreign-born.
Some of you have probably seen the latest statistics [link via Reuben] about the presence of foreign students in the US. There has been a steady decline since 9/11 that has made presidents of American universities sit up and take notice. Sometime last year, they asked for [sorry, no link!] a relaxation of visa policies (this year, there has certainly been an improvement in the visa procedures, and successful visa applications).
This op-ed, on the other hand, points out some of the other difficulties faced by foreign students once they get there for higher studies. In other words, visa procedures may have been the first trigger, but the current problems have been a result of many causes.