>There's really no "right" answer to how asynchronous courses should be.

Sure, but given Coursera's popularity it seems to be doing something right.

>On the other hand, if you run things on a tight schedule, real life will get in the way for a lot of people in that many of the better courses are fairly significant time commitments.

But is it? The time commitments are watching few videos, learning and doing the assignments, all of this in a week. I think it's enough even for people working full time. If you don't have enough time on your hands to do all this, I'd argue you don't have the time required to complete the course.

Furthermore having time constraints is very important for students to keep on track.