While there's somewhat of a culture of being "hardcore" and taking lots of classes at MIT, I find that many people abandon that mentality after their freshman year. In reality, most people are just trying to get by with the minimum 4 classes, which can already be a lot of work. The question is whether the others that have the intelligence/work ethic/time management skills/etc to take on more work are inclined to load up on more classes or take on side projects.
The answer depends a good deal on the kind of MIT subculture you live in. I live in a place where people like to build awesome things, and frankly, I feel a lot more guilty about not making enough time to hack on side projects than I do about not taking more classes.
On the other hand, in certain other dorms there are strong communities of math/cs/physics olympians, some of whom regularly take 8+ classes a semester.
The answer depends a good deal on the kind of MIT subculture you live in. I live in a place where people like to build awesome things, and frankly, I feel a lot more guilty about not making enough time to hack on side projects than I do about not taking more classes.
On the other hand, in certain other dorms there are strong communities of math/cs/physics olympians, some of whom regularly take 8+ classes a semester.