Reflecting on the violence in Bahrain, Joshua Tucker points out that successful revolutions often manage to avoid this sort of bloodshed:
For those of us who study protest from an individual based perspective (here and here for my own work on this) we are particularly interested in the costs and benefits to individual protesters of participating in protest. The first three of the original Colored Revolutions - Serbia, Georgia, and Ukraine - were conspicuous for their relative lack of violence and the fact that the military stayed out of the way of protesters, thus keeping the cost of protesting significantly lower; indeed, getting killed is the highest possible "cost" of protesting. (The fourth, the Kyrgyz Tulip Revolution, was a little more violent, but again the military restrained from a violent crackdown.) Both the Tunisian and Egyptian revolutions shared this characteristic of the military and (for the most part) the security services restraining from a violent crackdown.