I used the method in large groups and it has worked well for me, but there are other (psychological) elements you have to employ to make it do that. I have not been able to get it to work well with asynchronous online classes, however, because it is difficult to employ some of those elements and because the response times have too much of a lag to keep the conversation interesting or efficient. That could be overcome if students gave longer, more thorough answers each time, but most of them do not tend to do that, and I have not been able to get them to.