Great Depression 2.0, still ongoing, was triggered by foolish actions by a handful of big Wall Street operations. When a brain dead executive has control of massive amounts of cash, he can do a lot more damage than a similar executive at a smaller firm. When big outfits like Fannie Mae or AIG go belly up, Uncle Sam bails them out lest their failure throw the economy into a tail spin. This time Uncle spent carloads of cash bailing them out and the economy still tanked. Effective use of taxpayer funds that.
And, when us customers are shopping, we get a better deal if we have a lot competing companies to buy from. If a super biggie is the only game in town, we are going to get robbed.
So, for all these reasons, super big companies are a bad idea. We used to have a Sherman Anti Trust Act, enforced by the US justice department. Back in the good old days they broke up Standard Oil and the telephone company, and tried to break up IBM. Used to be, the Anti Trust division of Justice could put the kibosh on mergers if they deemed the merged company would be too big.
Far as I know, Sherman Anti Trust Act is still on the books, but the Justice department hasn't enforced it for 20 years or more. Which is why we have AIG and Microsoft out crashing the economy and abusing customers.
Let's bring back the Anti Trust lawyers and sic 'em on any company that controls more than 50% of any market.