Carrie,
You bring up some important issues in both types of online learning.
The students who "step out" during synchronous classes remind me of those who daydream or put their heads down during on campus classes. I deal with them online in much the same manner as I do on campus; I ask students to show their agreement with a statement I make by raising their hands. I include participation points as part of the grade in every class I teach.
I agree with you that asynchronous discussion can be less stressful, but I often have trouble getting students to offer meaningful or coplete answers to questions. Any suggestions?
Thanks,
Jane