Recently, the feds have bailed out Fannie Mae, Freddie Mac, Bear Sterns and AIG, all on the grounds that they were “too big to fail.” Here’s my question: why do we let these companies get too big? Seriously. The feds routinely review mergers between companies on anti-trust grounds. But do they ever say halt a merger on the grounds that the resulting company would be too big or vital to bail out if it came to that? It seems like a reasonable metric to use.