I think once serious study is undertaken on this important topic, we'll discover that non-violent revolution or insurgency is more dependent upon international reaction, duration (if it gets crushed quickly it won't linger in the media long enough to make a difference), the degree of popular support, and the righteousness of the cause (as viewed by the global community and the affected nation).

Tiananmen Square failed because it was quickly quashed, even after receiving considerable media attention. China didn't care about world opinion on how it managed its internal affairs, and a year later it was as though it never happened. The example in Poland is an excellent example, because the Solidarity Movement had a degree of popular support (whether or not it a majority or not can be argued, but they did mobilize politically). The Soviets did care about world opinion, so they had limited options, and the movement lasted for several months and was tied into a global network (the Catholic Church).

It works in some conditions, in others it won't stand a snow ball's chance in hell. Definitely worth the discussion, but it won't completely replace armed conflict anytime in the near future.