I think the advent of internet (directly or indirectly) has helped increase the number of foreign applicants. Lots of people in places like India were unaware of US Schools. Or even if they did they did not know the system and the processes to apply. However, now a single google seach for B'Schools (or as a matter of fact any type school) will show a whole list of potential schools, rankings and the process to apply etc.
I remember in the old days, we had to goto USIS to browse the guidebooks to research the schools and then write snail mails to request for admission package. The entire process took several days, if not months! Now it can be done in a few minutes, without paying a single dime (other than the internet connection charge)!
Also, the buying power of people in the progressive nations have also allowed them to even dream of schools here. Previously, the cost of school in the US itself was a turn off (especially with the conversion rates). Now with the increase in the living standards (indirectly due to the advancement of technology and the opportunities in the progressive nations) have allowed people from these states to consider education in the west.
The above in conjunction with the high competition for the IITs and the IIMs, especially, makes education in the west attractive thus driving up international applicants! I think this is just the starting and the trend is going to continue driving up the competition!