I don't see a need to travel outside the US during the MBA except for the following reasons..
1) International Exchange - I think most people oughta know if they will be participating in one before school starts
2) Leisure Travel - This is a good to have experience at a decent price. I'll be fine taking a trip to a place like Alaska/Hawaii if at all. It will be an awesome trip either way.
3) Internships/Projects - This is one place where the stamped VISA will definitely be handy and the only pressing reason for one to go back, other than wanting to spend quality time back home before school. I doubt that there are too many internships which make it mandatory for people to travel abroad. Most would be within the US and if you play your cards right you should be fine.
PS: At this point I am contemplating on getting through the 2 yr slot without getting the VISA "stamped"
However as I said, things might change once I am in school and I might end up going to India in the winter/spring break.
My 2 cents...
ujjib
...remember as bschoolers, you are gonna travel internationally quite a bit....
If you are going to a well known school, the risk of visa denial is going to be very very low..