It seems that the first lesson that should be learned from all of these "too big to fail" entities needing bailout is that there are other reasons to prevent me

It seems that the first lesson that should be learned from all of these "too big to fail" entities needing bailout is that there are other reasons to prevent mergers than just antitrust. If we prevented corporations above a certain size from growing (by merging), wouldn't these problems with mega-sized failures sending shock waves through the system be fixed? Maybe it would be less efficient, but it makes me think of a similar situation where pure profit-driven capitalism has lead to a bad situation: agricultural monocultures. Hunting for efficiency has produced a state that is finely tuned to be maximally efficient in the current environment while being dangerously sensitive to changes in that environment. It's just not prudent to go all out, even if you think you have a good hand... especially if you're gambling with your children's college funds...