And how many businesses do you estimate have been killed or eliminated because of unchecked m&a? Expanding the data set to include non-tech industries indicates strongly that it's not always the case that a big monopoly will eventually fail. Healthcare for example is filled with instances of bigger companies acquiring smaller ones and killing the competition to their product, a quick Google search will show you that.
Can you give me a specific example? Last I checked no insurer has more than 30% market share.